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SUNRPC: Add svc_rqst_replace_page() API

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[ Upstream commit 2f0f88f42f2eab0421ed37d7494de9124fdf0d34 ]

Replacing a page in rq_pages[] requires a get_page(), which is a
bus-locked operation, and a put_page(), which can be even more
costly.

To reduce the cost of replacing a page in rq_pages[], batch the
put_page() operations by collecting "freed" pages in a pagevec,
and then release those pages when the pagevec is full. This
pagevec is also emptied when each RPC completes.

[ cel: adjusted to apply without f6e70aab9dfe ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Chuck Lever 2021-07-01 10:03:10 -04:00 • committed by Ksawlii
parent e4c0565c98
commit 02094bf7cf
3 changed files with 28 additions and 0 deletions
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4
include/linux/sunrpc/svc.h
View file

@ -19,6 +19,7 @@
#include <linux/sunrpc/svcauth.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/pagevec.h>
/* statistics for svc_pool structures */
struct svc_pool_stats {
@ -256,6 +257,7 @@ struct svc_rqst {
struct page * *rq_next_page; /* next reply page to use */
struct page * *rq_page_end; /* one past the last page */
struct pagevec rq_pvec;
struct kvec rq_vec[RPCSVC_MAXPAGES]; /* generally useful.. */
struct bio_vec rq_bvec[RPCSVC_MAXPAGES];
@ -502,6 +504,8 @@ struct svc_rqst *svc_rqst_alloc(struct svc_serv *serv,
struct svc_pool *pool, int node);
struct svc_rqst *svc_prepare_thread(struct svc_serv *serv,
struct svc_pool *pool, int node);
void svc_rqst_replace_page(struct svc_rqst *rqstp,
struct page *page);
void svc_rqst_free(struct svc_rqst *);
void svc_exit_thread(struct svc_rqst *);
unsigned int svc_pool_map_get(void);

21
net/sunrpc/svc.c
View file

@ -842,6 +842,27 @@ svc_set_num_threads_sync(struct svc_serv *serv, struct svc_pool *pool, int nrser
}
EXPORT_SYMBOL_GPL(svc_set_num_threads_sync);
/**
* svc_rqst_replace_page - Replace one page in rq_pages[]
* @rqstp: svc_rqst with pages to replace
* @page: replacement page
*
* When replacing a page in rq_pages, batch the release of the
* replaced pages to avoid hammering the page allocator.
*/
void svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page)
{
if (*rqstp->rq_next_page) {
if (!pagevec_space(&rqstp->rq_pvec))
__pagevec_release(&rqstp->rq_pvec);
pagevec_add(&rqstp->rq_pvec, *rqstp->rq_next_page);
}
get_page(page);
*(rqstp->rq_next_page++) = page;
}
EXPORT_SYMBOL_GPL(svc_rqst_replace_page);
/*
* Called from a server thread as it's exiting. Caller must hold the "service
* mutex" for the service.

3
net/sunrpc/svc_xprt.c
View file

@ -525,6 +525,7 @@ static void svc_xprt_release(struct svc_rqst *rqstp)
kfree(rqstp->rq_deferred);
rqstp->rq_deferred = NULL;
pagevec_release(&rqstp->rq_pvec);
svc_free_res_pages(rqstp);
rqstp->rq_res.page_len = 0;
rqstp->rq_res.page_base = 0;
@ -651,6 +652,8 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
int pages;
int i;
pagevec_init(&rqstp->rq_pvec);
/* now allocate needed pages. If we get a failure, sleep briefly */
pages = (serv->sv_max_mesg + 2 * PAGE_SIZE) >> PAGE_SHIFT;
if (pages > RPCSVC_MAXPAGES) {