| Message ID | 20180913214102.28269-3-timofey.titovets@synesis.ru (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Currently used jhash are slow enough and replace it allow as to make KSM | expand |
On Fri, Sep 14, 2018 at 12:41:02AM +0300, Timofey Titovets wrote: > From: Timofey Titovets <nefelim4ag@gmail.com> > > Replace jhash2 with xxhash. > > Perf numbers: > Intel(R) Xeon(R) CPU E5-2420 v2 @ 2.20GHz > ksm: crc32c hash() 12081 MB/s > ksm: xxh64 hash() 8770 MB/s > ksm: xxh32 hash() 4529 MB/s > ksm: jhash2 hash() 1569 MB/s > > From Sioh Lee: > crc32c_intel: 1084.10ns > crc32c (no hardware acceleration): 7012.51ns > xxhash32: 2227.75ns > xxhash64: 1413.16ns > jhash2: 5128.30ns > > As jhash2 always will be slower (for data size like PAGE_SIZE). > Don't use it in ksm at all. > > Use only xxhash for now, because for using crc32c, > cryptoapi must be initialized first - that require some > tricky solution to work good in all situations. > > Thanks. > > Changes: > v1 -> v2: > - Move xxhash() to xxhash.h/c and separate patches > v2 -> v3: > - Move xxhash() xxhash.c -> xxhash.h > - replace xxhash_t with 'unsigned long' > - update kerneldoc above xxhash() > v3 -> v4: > - Merge xxhash/crc32 patches > - Replace crc32 with crc32c (crc32 have same as jhash2 speed) > - Add auto speed test and auto choice of fastest hash function > v4 -> v5: > - Pickup missed xxhash patch > - Update code with compile time choicen xxhash > - Add more macros to make code more readable > - As now that only possible use xxhash or crc32c, > on crc32c allocation error, skip speed test and fallback to xxhash > - For workaround too early init problem (crc32c not avaliable), > move zero_checksum init to first call of fastcall() > - Don't alloc page for hash testing, use arch zero pages for that > v5 -> v6: > - Use libcrc32c instead of CRYPTO API, mainly for > code/Kconfig deps Simplification > - Add crc32c_available(): > libcrc32c will BUG_ON on crc32c problems, > so test crc32c avaliable by crc32c_available() > - Simplify choice_fastest_hash() > - Simplify fasthash() > - struct rmap_item && stable_node have sizeof == 64 on x86_64, > that makes them cache friendly. As we don't suffer from hash collisions, > change hash type from unsigned long back to u32. > - Fix kbuild robot warning, make all local functions static > v6 -> v7: > - Drop crc32c for now and use only xxhash in ksm. > v7 -> v8: > - Remove empty line changes > > Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com> > Signed-off-by: leesioh <solee@os.korea.ac.kr> > Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com> Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com> > CC: Andrea Arcangeli <aarcange@redhat.com> > CC: linux-mm@kvack.org > CC: kvm@vger.kernel.org > --- > mm/Kconfig | 1 + > mm/ksm.c | 4 ++-- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/mm/Kconfig b/mm/Kconfig > index a550635ea5c3..b5f923081bce 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -297,6 +297,7 @@ config MMU_NOTIFIER > config KSM > bool "Enable KSM for page merging" > depends on MMU > + select XXHASH > help > Enable Kernel Samepage Merging: KSM periodically scans those areas > of an application's address space that an app has advised may be > diff --git a/mm/ksm.c b/mm/ksm.c > index 5b0894b45ee5..1a088306ef81 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -25,7 +25,7 @@ > #include <linux/pagemap.h> > #include <linux/rmap.h> > #include <linux/spinlock.h> > -#include <linux/jhash.h> > +#include <linux/xxhash.h> > #include <linux/delay.h> > #include <linux/kthread.h> > #include <linux/wait.h> > @@ -1009,7 +1009,7 @@ static u32 calc_checksum(struct page *page) > { > u32 checksum; > void *addr = kmap_atomic(page); > - checksum = jhash2(addr, PAGE_SIZE / 4, 17); > + checksum = xxhash(addr, PAGE_SIZE, 0); > kunmap_atomic(addr); > return checksum; > } > -- > 2.19.0 >
diff --git a/mm/Kconfig b/mm/Kconfig index a550635ea5c3..b5f923081bce 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -297,6 +297,7 @@ config MMU_NOTIFIER config KSM bool "Enable KSM for page merging" depends on MMU + select XXHASH help Enable Kernel Samepage Merging: KSM periodically scans those areas of an application's address space that an app has advised may be diff --git a/mm/ksm.c b/mm/ksm.c index 5b0894b45ee5..1a088306ef81 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -25,7 +25,7 @@ #include <linux/pagemap.h> #include <linux/rmap.h> #include <linux/spinlock.h> -#include <linux/jhash.h> +#include <linux/xxhash.h> #include <linux/delay.h> #include <linux/kthread.h> #include <linux/wait.h> @@ -1009,7 +1009,7 @@ static u32 calc_checksum(struct page *page) { u32 checksum; void *addr = kmap_atomic(page); - checksum = jhash2(addr, PAGE_SIZE / 4, 17); + checksum = xxhash(addr, PAGE_SIZE, 0); kunmap_atomic(addr); return checksum; }