From 0e749e54244eec87b2a3cd0a4314e60bc6781115 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 15 Jan 2016 16:55:53 -0800 Subject: [PATCH] dax: increase granularity of dax_clear_blocks() operations dax_clear_blocks is currently performing a cond_resched() after every PAGE_SIZE memset. We need not check so frequently, for example md-raid only calls cond_resched() at stripe granularity. Also, in preparation for introducing a dax_map_atomic() operation that temporarily pins a dax mapping move the call to cond_resched() to the outer loop. The worst case latency between calls to cond_resched() after this change is 500us the average latency is 133us. This is up from a 10us max and 4us average. Signed-off-by: Dan Williams Reviewed-by: Jan Kara Reviewed-by: Jeff Moyer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/dax.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 19492cc65a30..11721c0fc127 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -28,6 +28,7 @@ #include #include #include +#include /* * dax_clear_blocks() is called from within transaction context from XFS, @@ -43,24 +44,17 @@ int dax_clear_blocks(struct inode *inode, sector_t block, long size) do { void __pmem *addr; unsigned long pfn; - long count; + long count, sz; count = bdev_direct_access(bdev, sector, &addr, &pfn, size); if (count < 0) return count; - BUG_ON(size < count); - while (count > 0) { - unsigned pgsz = PAGE_SIZE - offset_in_page(addr); - if (pgsz > count) - pgsz = count; - clear_pmem(addr, pgsz); - addr += pgsz; - size -= pgsz; - count -= pgsz; - BUG_ON(pgsz & 511); - sector += pgsz / 512; - cond_resched(); - } + sz = min_t(long, count, SZ_128K); + clear_pmem(addr, sz); + size -= sz; + BUG_ON(sz & 511); + sector += sz / 512; + cond_resched(); } while (size); wmb_pmem(); -- 2.20.1