From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Simmons Date: Mon, 5 Oct 2020 20:05:42 -0400 Subject: [lustre-devel] [PATCH 03/42] lustre: sec: use memchr_inv() to check if page is zero. In-Reply-To: <1601942781-24950-1-git-send-email-jsimmons@infradead.org> References: <1601942781-24950-1-git-send-email-jsimmons@infradead.org> Message-ID: <1601942781-24950-4-git-send-email-jsimmons@infradead.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org From: Mr NeilBrown memchr_inv() is the preferred way to check if a memory region is all zeros. It is likely fast that memcmp() is it doesn't need to read the ZERO_PAGE into cache, or into the CPU. It was introduced in Linux 3.2. WC-bug-id: https://jira.whamcloud.com/browse/LU-12275 Lustre-commit: afee2380c105c ("LU-12275 sec: use memchr_inv() to check if page is zero.") Signed-off-by: Mr NeilBrown Reviewed-on: https://review.whamcloud.com/39459 Reviewed-by: Andreas Dilger Reviewed-by: James Simmons Reviewed-by: Sebastien Buisson Signed-off-by: James Simmons --- fs/lustre/osc/osc_request.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/fs/lustre/osc/osc_request.c b/fs/lustre/osc/osc_request.c index 1e56ca3..fbb8453 100644 --- a/fs/lustre/osc/osc_request.c +++ b/fs/lustre/osc/osc_request.c @@ -2077,9 +2077,8 @@ static int osc_brw_fini_request(struct ptlrpc_request *req, int rc) struct brw_page *pg = aa->aa_ppga[idx]; /* do not decrypt if page is all 0s */ - if (memcmp(page_address(pg->pg), - page_address(ZERO_PAGE(0)), - PAGE_SIZE) == 0) { + if (memchr_inv(page_address(pg->pg), 0, + PAGE_SIZE) == NULL) { /* if page is empty forward info to upper layers * (ll_io_zero_page) by clearing PagePrivate2 */ -- 1.8.3.1