| Message ID | 20210705145547.41206-1-urezki@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/vmalloc: Use batched page requests in bulk-allocator | expand |
On Mon, Jul 05, 2021 at 04:55:47PM +0200, Uladzislau Rezki (Sony) wrote: > + if (gfpflags_allow_blocking(gfp)) > + cond_resched(); How does one call vmalloc() with gfp flags that _don't_ allow blocking? They have to allow a GFP_KERNEL allocation of the page tables. So I think this should be an unconditional cond_resched().
> On Mon, Jul 05, 2021 at 04:55:47PM +0200, Uladzislau Rezki (Sony) wrote: > > + if (gfpflags_allow_blocking(gfp)) > > + cond_resched(); > > How does one call vmalloc() with gfp flags that _don't_ allow blocking? > They have to allow a GFP_KERNEL allocation of the page tables. > So I think this should be an unconditional cond_resched(). Historically it is there. I decided to align with below code. But i agree vmalloc is sleepable anyway, so blocking is supposed. OK, i will respin and send out two patches. -- Vlad Rezki
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index aaad569e8963..01ad46f97365 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2785,10 +2785,34 @@ vm_area_alloc_pages(gfp_t gfp, int nid, * to fails, fallback to a single page allocator that is * more permissive. */ - if (!order) - nr_allocated = alloc_pages_bulk_array_node( - gfp, nid, nr_pages, pages); - else + if (!order) { + while (nr_allocated < nr_pages) { + int nr, nr_pages_request; + + /* + * A maximum allowed request is hard-coded and is 100 + * pages per call. That is done in order to prevent a + * long preemption off scenario in the bulk-allocator + * so the range is [1:100]. + */ + nr_pages_request = min(100, (int)(nr_pages - nr_allocated)); + + nr = alloc_pages_bulk_array_node(gfp, nid, + nr_pages_request, pages + nr_allocated); + + nr_allocated += nr; + + if (gfpflags_allow_blocking(gfp)) + cond_resched(); + + /* + * If zero or pages were obtained partly, + * fallback to a single page allocator. + */ + if (nr != nr_pages_request) + break; + } + } else /* * Compound pages required for remap_vmalloc_page if * high-order pages.
In case of simultaneous vmalloc allocations, for example it is 1GB and 12 CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT kernel. <snip> [ 62.512621] RIP: 0010:__alloc_pages_bulk+0xa9f/0xbb0 [ 62.512628] Code: ff 8b 44 24 48 44 29 f8 83 f8 01 0f 84 ea fe ff ff e9 07 f6 ff ff 48 8b 44 24 60 48 89 28 e9 00 f9 ff ff fb 66 0f 1f 44 00 00 <e9> e8 fd ff ff 65 48 01 51 10 e9 3e fe ff ff 48 8b 44 24 78 4d 89 [ 62.512629] RSP: 0018:ffffa7bfc29ffd20 EFLAGS: 00000206 [ 62.512631] RAX: 0000000000000200 RBX: ffffcd5405421888 RCX: ffff8c36ffdeb928 [ 62.512632] RDX: 0000000000040000 RSI: ffffa896f06b2ff8 RDI: ffffcd5405421880 [ 62.512633] RBP: ffffcd5405421880 R08: 000000000000007d R09: ffffffffffffffff [ 62.512634] R10: ffffffff9d63c084 R11: 00000000ffffffff R12: ffff8c373ffaeb80 [ 62.512635] R13: ffff8c36ffdf65f8 R14: ffff8c373ffaeb80 R15: 0000000000040000 [ 62.512637] FS: 0000000000000000(0000) GS:ffff8c36ffdc0000(0000) knlGS:0000000000000000 [ 62.512638] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 62.512639] CR2: 000055c8e2fe8610 CR3: 0000000c13e10000 CR4: 00000000000006e0 [ 62.512641] Call Trace: [ 62.512646] __vmalloc_node_range+0x11c/0x2d0 [ 62.512649] ? full_fit_alloc_test+0x140/0x140 [test_vmalloc] [ 62.512654] __vmalloc_node+0x4b/0x70 [ 62.512656] ? fix_size_alloc_test+0x44/0x60 [test_vmalloc] [ 62.512659] fix_size_alloc_test+0x44/0x60 [test_vmalloc] [ 62.512662] test_func+0xe7/0x1f0 [test_vmalloc] [ 62.512666] ? fix_align_alloc_test+0x50/0x50 [test_vmalloc] [ 62.512668] kthread+0x11a/0x140 [ 62.512671] ? set_kthread_struct+0x40/0x40 [ 62.512672] ret_from_fork+0x22/0x30 <snip> To address this issue invoke a bulk-allocator many times until all pages are obtained, i.e. do batched page requests adding cond_resched() meanwhile to reschedule. Batched value is hard-coded and is 100 pages per call. Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> --- mm/vmalloc.c | 32 ++++++++++++++++++++++++++++---- 1 file changed, 28 insertions(+), 4 deletions(-)