From 7578b2f628db27281d3165af0aa862311883a858 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Thu, 30 Sep 2021 19:10:03 -0400 Subject: NFSD: Remove be32_to_cpu() from DRC hash function Commit 7142b98d9fd7 ("nfsd: Clean up drc cache in preparation for global spinlock elimination"), billed as a clean-up, added be32_to_cpu() to the DRC hash function without explanation. That commit removed two comments that state that byte-swapping in the hash function is unnecessary without explaining whether there was a need for that change. On some Intel CPUs, the swab32 instruction is known to cause a CPU pipeline stall. be32_to_cpu() does not add extra randomness, since the hash multiplication is done /before/ shifting to the high-order bits of the result. As a micro-optimization, remove the unnecessary transform from the DRC hash function. Signed-off-by: Chuck Lever --- fs/nfsd/nfscache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c index 6e0b6f3148dc..a4a69ab6ab28 100644 --- a/fs/nfsd/nfscache.c +++ b/fs/nfsd/nfscache.c @@ -87,7 +87,7 @@ nfsd_hashsize(unsigned int limit) static u32 nfsd_cache_hash(__be32 xid, struct nfsd_net *nn) { - return hash_32(be32_to_cpu(xid), nn->maskbits); + return hash_32((__force u32)xid, nn->maskbits); } static struct svc_cacherep * -- cgit v1.2.3-59-g8ed1b