| Message ID | 20240125164256.4147-7-alexandru.elisei@arm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for arm64 MTE dynamic tag storage reuse | expand |
On 1/25/24 22:12, Alexandru Elisei wrote: > The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one > after each cma_alloc() function call. This is done even though cma_alloc() > can allocate an arbitrary number of CMA pages. When looking at > /proc/vmstat, the number of successful (or failed) cma_alloc() calls > doesn't tell much with regards to how many CMA pages were allocated via > cma_alloc() versus via the page allocator (regular allocation request or > PCP lists refill). > > This can also be rather confusing to a user who isn't familiar with the > code, since the unit of measurement for nr_free_cma is the number of pages, > but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() > function calls. > > Let's make this consistent, and arguably more useful, by having > CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and > CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to > allocate. > > For users that wish to track the number of cma_alloc() calls, there are > tracepoints for that already implemented. > > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > --- > mm/cma.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/cma.c b/mm/cma.c > index f49c95f8ee37..dbf7fe8cb1bd 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, > pr_debug("%s(): returned %p\n", __func__, page); > out: > if (page) { > - count_vm_event(CMA_ALLOC_SUCCESS); > + count_vm_events(CMA_ALLOC_SUCCESS, count); > cma_sysfs_account_success_pages(cma, count); > } else { > - count_vm_event(CMA_ALLOC_FAIL); > + count_vm_events(CMA_ALLOC_FAIL, count); > if (cma) > cma_sysfs_account_fail_pages(cma, count); > } Without getting into the merits of this patch - which is actually trying to do semantics change to /proc/vmstat, wondering how is this even related to this particular series ? If required this could be debated on it's on separately.
Hi, On Mon, Jan 29, 2024 at 02:54:20PM +0530, Anshuman Khandual wrote: > > > On 1/25/24 22:12, Alexandru Elisei wrote: > > The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one > > after each cma_alloc() function call. This is done even though cma_alloc() > > can allocate an arbitrary number of CMA pages. When looking at > > /proc/vmstat, the number of successful (or failed) cma_alloc() calls > > doesn't tell much with regards to how many CMA pages were allocated via > > cma_alloc() versus via the page allocator (regular allocation request or > > PCP lists refill). > > > > This can also be rather confusing to a user who isn't familiar with the > > code, since the unit of measurement for nr_free_cma is the number of pages, > > but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() > > function calls. > > > > Let's make this consistent, and arguably more useful, by having > > CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and > > CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to > > allocate. > > > > For users that wish to track the number of cma_alloc() calls, there are > > tracepoints for that already implemented. > > > > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > > --- > > mm/cma.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/mm/cma.c b/mm/cma.c > > index f49c95f8ee37..dbf7fe8cb1bd 100644 > > --- a/mm/cma.c > > +++ b/mm/cma.c > > @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, > > pr_debug("%s(): returned %p\n", __func__, page); > > out: > > if (page) { > > - count_vm_event(CMA_ALLOC_SUCCESS); > > + count_vm_events(CMA_ALLOC_SUCCESS, count); > > cma_sysfs_account_success_pages(cma, count); > > } else { > > - count_vm_event(CMA_ALLOC_FAIL); > > + count_vm_events(CMA_ALLOC_FAIL, count); > > if (cma) > > cma_sysfs_account_fail_pages(cma, count); > > } > > Without getting into the merits of this patch - which is actually trying to do > semantics change to /proc/vmstat, wondering how is this even related to this > particular series ? If required this could be debated on it's on separately. Having the number of CMA pages allocated and the number of CMA pages freed allows someone to infer how many tagged pages are in use at a given time: (allocated CMA pages - CMA pages allocated by drivers* - CMA pages released) * 32. That is valuable information for software and hardware designers. Besides that, for every iteration of the series, this has proven invaluable for discovering bugs with freeing and/or reserving tag storage pages. *that would require userspace reading cma_alloc_success and cma_release_success before any tagged allocations are performed. Thanks, Alex
On 1/29/24 17:21, Alexandru Elisei wrote: > Hi, > > On Mon, Jan 29, 2024 at 02:54:20PM +0530, Anshuman Khandual wrote: >> >> >> On 1/25/24 22:12, Alexandru Elisei wrote: >>> The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one >>> after each cma_alloc() function call. This is done even though cma_alloc() >>> can allocate an arbitrary number of CMA pages. When looking at >>> /proc/vmstat, the number of successful (or failed) cma_alloc() calls >>> doesn't tell much with regards to how many CMA pages were allocated via >>> cma_alloc() versus via the page allocator (regular allocation request or >>> PCP lists refill). >>> >>> This can also be rather confusing to a user who isn't familiar with the >>> code, since the unit of measurement for nr_free_cma is the number of pages, >>> but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() >>> function calls. >>> >>> Let's make this consistent, and arguably more useful, by having >>> CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and >>> CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to >>> allocate. >>> >>> For users that wish to track the number of cma_alloc() calls, there are >>> tracepoints for that already implemented. >>> >>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> >>> --- >>> mm/cma.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/cma.c b/mm/cma.c >>> index f49c95f8ee37..dbf7fe8cb1bd 100644 >>> --- a/mm/cma.c >>> +++ b/mm/cma.c >>> @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, >>> pr_debug("%s(): returned %p\n", __func__, page); >>> out: >>> if (page) { >>> - count_vm_event(CMA_ALLOC_SUCCESS); >>> + count_vm_events(CMA_ALLOC_SUCCESS, count); >>> cma_sysfs_account_success_pages(cma, count); >>> } else { >>> - count_vm_event(CMA_ALLOC_FAIL); >>> + count_vm_events(CMA_ALLOC_FAIL, count); >>> if (cma) >>> cma_sysfs_account_fail_pages(cma, count); >>> } >> >> Without getting into the merits of this patch - which is actually trying to do >> semantics change to /proc/vmstat, wondering how is this even related to this >> particular series ? If required this could be debated on it's on separately. > > Having the number of CMA pages allocated and the number of CMA pages freed > allows someone to infer how many tagged pages are in use at a given time: That should not be done in CMA which is a generic multi purpose allocator. > (allocated CMA pages - CMA pages allocated by drivers* - CMA pages > released) * 32. That is valuable information for software and hardware > designers. > > Besides that, for every iteration of the series, this has proven invaluable > for discovering bugs with freeing and/or reserving tag storage pages. I am afraid that might not be enough justification for getting something merged mainline. > > *that would require userspace reading cma_alloc_success and > cma_release_success before any tagged allocations are performed. While assuming that no other non-memory-tagged CMA based allocation amd free call happens in the meantime ? That would be on real thin ice. I suppose arm64 tagged memory specific allocation or free related counters need to be created on the caller side, including arch_free_pages_prepare().
Hi, On Tue, Jan 30, 2024 at 10:22:11AM +0530, Anshuman Khandual wrote: > > > On 1/29/24 17:21, Alexandru Elisei wrote: > > Hi, > > > > On Mon, Jan 29, 2024 at 02:54:20PM +0530, Anshuman Khandual wrote: > >> > >> > >> On 1/25/24 22:12, Alexandru Elisei wrote: > >>> The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one > >>> after each cma_alloc() function call. This is done even though cma_alloc() > >>> can allocate an arbitrary number of CMA pages. When looking at > >>> /proc/vmstat, the number of successful (or failed) cma_alloc() calls > >>> doesn't tell much with regards to how many CMA pages were allocated via > >>> cma_alloc() versus via the page allocator (regular allocation request or > >>> PCP lists refill). > >>> > >>> This can also be rather confusing to a user who isn't familiar with the > >>> code, since the unit of measurement for nr_free_cma is the number of pages, > >>> but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() > >>> function calls. > >>> > >>> Let's make this consistent, and arguably more useful, by having > >>> CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and > >>> CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to > >>> allocate. > >>> > >>> For users that wish to track the number of cma_alloc() calls, there are > >>> tracepoints for that already implemented. > >>> > >>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > >>> --- > >>> mm/cma.c | 4 ++-- > >>> 1 file changed, 2 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/mm/cma.c b/mm/cma.c > >>> index f49c95f8ee37..dbf7fe8cb1bd 100644 > >>> --- a/mm/cma.c > >>> +++ b/mm/cma.c > >>> @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, > >>> pr_debug("%s(): returned %p\n", __func__, page); > >>> out: > >>> if (page) { > >>> - count_vm_event(CMA_ALLOC_SUCCESS); > >>> + count_vm_events(CMA_ALLOC_SUCCESS, count); > >>> cma_sysfs_account_success_pages(cma, count); > >>> } else { > >>> - count_vm_event(CMA_ALLOC_FAIL); > >>> + count_vm_events(CMA_ALLOC_FAIL, count); > >>> if (cma) > >>> cma_sysfs_account_fail_pages(cma, count); > >>> } > >> > >> Without getting into the merits of this patch - which is actually trying to do > >> semantics change to /proc/vmstat, wondering how is this even related to this > >> particular series ? If required this could be debated on it's on separately. > > > > Having the number of CMA pages allocated and the number of CMA pages freed > > allows someone to infer how many tagged pages are in use at a given time: > > That should not be done in CMA which is a generic multi purpose allocator. Ah, ok. Let me rephrase that: Having the number of CMA pages allocated, the number of failed CMA page allocations and the number of freed CMA pages allows someone to infer how many CMA pages are in use at a given time. That's valuable information for software designers and system administrators, as it allows them to tune the number of CMA pages available in a system. Or put another way: what would you consider to be more useful? Knowing the number of cma_alloc()/cma_release() calls, or knowing the number of pages that cma_alloc()/cma_release() allocated or freed? > > > (allocated CMA pages - CMA pages allocated by drivers* - CMA pages > > released) * 32. That is valuable information for software and hardware > > designers. > > > > Besides that, for every iteration of the series, this has proven invaluable > > for discovering bugs with freeing and/or reserving tag storage pages. > > I am afraid that might not be enough justification for getting something > merged mainline. > > > > > *that would require userspace reading cma_alloc_success and > > cma_release_success before any tagged allocations are performed. > > While assuming that no other non-memory-tagged CMA based allocation amd free > call happens in the meantime ? That would be on real thin ice. > > I suppose arm64 tagged memory specific allocation or free related counters > need to be created on the caller side, including arch_free_pages_prepare(). I'll think about this. At the very least, I can add tracepoints. Thanks, Alex
On 1/30/24 17:28, Alexandru Elisei wrote: > Hi, > > On Tue, Jan 30, 2024 at 10:22:11AM +0530, Anshuman Khandual wrote: >> >> On 1/29/24 17:21, Alexandru Elisei wrote: >>> Hi, >>> >>> On Mon, Jan 29, 2024 at 02:54:20PM +0530, Anshuman Khandual wrote: >>>> >>>> On 1/25/24 22:12, Alexandru Elisei wrote: >>>>> The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one >>>>> after each cma_alloc() function call. This is done even though cma_alloc() >>>>> can allocate an arbitrary number of CMA pages. When looking at >>>>> /proc/vmstat, the number of successful (or failed) cma_alloc() calls >>>>> doesn't tell much with regards to how many CMA pages were allocated via >>>>> cma_alloc() versus via the page allocator (regular allocation request or >>>>> PCP lists refill). >>>>> >>>>> This can also be rather confusing to a user who isn't familiar with the >>>>> code, since the unit of measurement for nr_free_cma is the number of pages, >>>>> but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() >>>>> function calls. >>>>> >>>>> Let's make this consistent, and arguably more useful, by having >>>>> CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and >>>>> CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to >>>>> allocate. >>>>> >>>>> For users that wish to track the number of cma_alloc() calls, there are >>>>> tracepoints for that already implemented. >>>>> >>>>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> >>>>> --- >>>>> mm/cma.c | 4 ++-- >>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/mm/cma.c b/mm/cma.c >>>>> index f49c95f8ee37..dbf7fe8cb1bd 100644 >>>>> --- a/mm/cma.c >>>>> +++ b/mm/cma.c >>>>> @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, >>>>> pr_debug("%s(): returned %p\n", __func__, page); >>>>> out: >>>>> if (page) { >>>>> - count_vm_event(CMA_ALLOC_SUCCESS); >>>>> + count_vm_events(CMA_ALLOC_SUCCESS, count); >>>>> cma_sysfs_account_success_pages(cma, count); >>>>> } else { >>>>> - count_vm_event(CMA_ALLOC_FAIL); >>>>> + count_vm_events(CMA_ALLOC_FAIL, count); >>>>> if (cma) >>>>> cma_sysfs_account_fail_pages(cma, count); >>>>> } >>>> Without getting into the merits of this patch - which is actually trying to do >>>> semantics change to /proc/vmstat, wondering how is this even related to this >>>> particular series ? If required this could be debated on it's on separately. >>> Having the number of CMA pages allocated and the number of CMA pages freed >>> allows someone to infer how many tagged pages are in use at a given time: >> That should not be done in CMA which is a generic multi purpose allocator. > Ah, ok. Let me rephrase that: Having the number of CMA pages allocated, the > number of failed CMA page allocations and the number of freed CMA pages > allows someone to infer how many CMA pages are in use at a given time. > That's valuable information for software designers and system > administrators, as it allows them to tune the number of CMA pages available > in a system. > > Or put another way: what would you consider to be more useful? Knowing the > number of cma_alloc()/cma_release() calls, or knowing the number of pages > that cma_alloc()/cma_release() allocated or freed? There is still value in knowing how many times cma_alloc() succeeded or failed regardless of the cumulative number pages involved over the time. Actually the count helps to understand how cma_alloc() performed overall as an allocator. But on the cma_release() path there is no chances of failure apart from - just when the caller itself provides an wrong input. So there are no corresponding CMA_RELEASE_SUCCESS/CMA_RELEASE_FAIL vmstat counters in there - for a reason ! Coming back to CMA based pages being allocated and freed, there is already an interface via sysfs (CONFIG_CMA_SYSFS) which gets updated in cma_alloc() path via cma_sysfs_account_success_pages() and cma_sysfs_account_fail_pages(). #ls /sys/kernel/mm/cma/<name> alloc_pages_fail alloc_pages_success Why these counters could not meet your requirements ? Also 'struct cma' can be updated to add an element 'nr_pages_freed' to be tracked in cma_release(), providing free pages count as well. There are additional debug fs based elements (CONFIG_CMA_DEBUGFS) available. #ls /sys/kernel/debug/cma/<name> alloc base_pfn bitmap count free maxchunk order_per_bit used
Hi, On Wed, Jan 31, 2024 at 10:10:05AM +0530, Anshuman Khandual wrote: > > > On 1/30/24 17:28, Alexandru Elisei wrote: > > Hi, > > > > On Tue, Jan 30, 2024 at 10:22:11AM +0530, Anshuman Khandual wrote: > >> > >> On 1/29/24 17:21, Alexandru Elisei wrote: > >>> Hi, > >>> > >>> On Mon, Jan 29, 2024 at 02:54:20PM +0530, Anshuman Khandual wrote: > >>>> > >>>> On 1/25/24 22:12, Alexandru Elisei wrote: > >>>>> The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one > >>>>> after each cma_alloc() function call. This is done even though cma_alloc() > >>>>> can allocate an arbitrary number of CMA pages. When looking at > >>>>> /proc/vmstat, the number of successful (or failed) cma_alloc() calls > >>>>> doesn't tell much with regards to how many CMA pages were allocated via > >>>>> cma_alloc() versus via the page allocator (regular allocation request or > >>>>> PCP lists refill). > >>>>> > >>>>> This can also be rather confusing to a user who isn't familiar with the > >>>>> code, since the unit of measurement for nr_free_cma is the number of pages, > >>>>> but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() > >>>>> function calls. > >>>>> > >>>>> Let's make this consistent, and arguably more useful, by having > >>>>> CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and > >>>>> CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to > >>>>> allocate. > >>>>> > >>>>> For users that wish to track the number of cma_alloc() calls, there are > >>>>> tracepoints for that already implemented. > >>>>> > >>>>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > >>>>> --- > >>>>> mm/cma.c | 4 ++-- > >>>>> 1 file changed, 2 insertions(+), 2 deletions(-) > >>>>> > >>>>> diff --git a/mm/cma.c b/mm/cma.c > >>>>> index f49c95f8ee37..dbf7fe8cb1bd 100644 > >>>>> --- a/mm/cma.c > >>>>> +++ b/mm/cma.c > >>>>> @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, > >>>>> pr_debug("%s(): returned %p\n", __func__, page); > >>>>> out: > >>>>> if (page) { > >>>>> - count_vm_event(CMA_ALLOC_SUCCESS); > >>>>> + count_vm_events(CMA_ALLOC_SUCCESS, count); > >>>>> cma_sysfs_account_success_pages(cma, count); > >>>>> } else { > >>>>> - count_vm_event(CMA_ALLOC_FAIL); > >>>>> + count_vm_events(CMA_ALLOC_FAIL, count); > >>>>> if (cma) > >>>>> cma_sysfs_account_fail_pages(cma, count); > >>>>> } > >>>> Without getting into the merits of this patch - which is actually trying to do > >>>> semantics change to /proc/vmstat, wondering how is this even related to this > >>>> particular series ? If required this could be debated on it's on separately. > >>> Having the number of CMA pages allocated and the number of CMA pages freed > >>> allows someone to infer how many tagged pages are in use at a given time: > >> That should not be done in CMA which is a generic multi purpose allocator. > > > Ah, ok. Let me rephrase that: Having the number of CMA pages allocated, the > > number of failed CMA page allocations and the number of freed CMA pages > > allows someone to infer how many CMA pages are in use at a given time. > > That's valuable information for software designers and system > > administrators, as it allows them to tune the number of CMA pages available > > in a system. > > > > Or put another way: what would you consider to be more useful? Knowing the > > number of cma_alloc()/cma_release() calls, or knowing the number of pages > > that cma_alloc()/cma_release() allocated or freed? > > There is still value in knowing how many times cma_alloc() succeeded or failed > regardless of the cumulative number pages involved over the time. Actually the > count helps to understand how cma_alloc() performed overall as an allocator. > > But on the cma_release() path there is no chances of failure apart from - just > when the caller itself provides an wrong input. So there are no corresponding > CMA_RELEASE_SUCCESS/CMA_RELEASE_FAIL vmstat counters in there - for a reason ! > > Coming back to CMA based pages being allocated and freed, there is already an > interface via sysfs (CONFIG_CMA_SYSFS) which gets updated in cma_alloc() path > via cma_sysfs_account_success_pages() and cma_sysfs_account_fail_pages(). > > #ls /sys/kernel/mm/cma/<name> > alloc_pages_fail alloc_pages_success > > Why these counters could not meet your requirements ? Also 'struct cma' can > be updated to add an element 'nr_pages_freed' to be tracked in cma_release(), > providing free pages count as well. > > There are additional debug fs based elements (CONFIG_CMA_DEBUGFS) available. > > #ls /sys/kernel/debug/cma/<name> > alloc base_pfn bitmap count free maxchunk order_per_bit used Ok, I'll have a look at those, thank you for the suggestion. Thanks, Alex
diff --git a/mm/cma.c b/mm/cma.c index f49c95f8ee37..dbf7fe8cb1bd 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, pr_debug("%s(): returned %p\n", __func__, page); out: if (page) { - count_vm_event(CMA_ALLOC_SUCCESS); + count_vm_events(CMA_ALLOC_SUCCESS, count); cma_sysfs_account_success_pages(cma, count); } else { - count_vm_event(CMA_ALLOC_FAIL); + count_vm_events(CMA_ALLOC_FAIL, count); if (cma) cma_sysfs_account_fail_pages(cma, count); }
The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one after each cma_alloc() function call. This is done even though cma_alloc() can allocate an arbitrary number of CMA pages. When looking at /proc/vmstat, the number of successful (or failed) cma_alloc() calls doesn't tell much with regards to how many CMA pages were allocated via cma_alloc() versus via the page allocator (regular allocation request or PCP lists refill). This can also be rather confusing to a user who isn't familiar with the code, since the unit of measurement for nr_free_cma is the number of pages, but cma_alloc_success and cma_alloc_fail count the number of cma_alloc() function calls. Let's make this consistent, and arguably more useful, by having CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and CMA_ALLOC_FAIL count the number of pages the cma_alloc() failed to allocate. For users that wish to track the number of cma_alloc() calls, there are tracepoints for that already implemented. Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> --- mm/cma.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)