Commit 91a76be3 authored by Dominique Martinet's avatar Dominique Martinet
Browse files

9p: add a per-client fcall kmem_cache 

Having a specific cache for the fcall allocations helps speed up
end-to-end latency.

The caches will automatically be merged if there are multiple caches
of items with the same size so we do not need to try to share a cache
between different clients of the same size.

Since the msize is negotiated with the server, only allocate the cache
after that negotiation has happened - previous allocations or
allocations of different sizes (e.g. zero-copy fcall) are made with
kmalloc directly.

Some figures on two beefy VMs with Connect-IB (sriov) / trans=rdma,
with ior running 32 processes in parallel doing small 32 bytes IOs:
 - no alloc (4.18-rc7 request cache): 65.4k req/s
 - non-power of two alloc, no patch: 61.6k req/s
 - power of two alloc, no patch: 62.2k req/s
 - non-power of two alloc, with patch: 64.7k req/s
 - power of two alloc, with patch: 65.1k req/s

Link: http://lkml.kernel.org/r/1532943263-24378-2-git-send-email-asmadeus@codewreck.org


Signed-off-by: default avatarDominique Martinet <dominique.martinet@cea.fr>
Acked-by: default avatarJun Piao <piaojun@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Greg Kurz <groug@kaod.org>
parent 523adb6c

include/net/9p/9p.h

+4 −0
Original line number Diff line number Diff line
@@ -336,6 +336,9 @@ enum p9_qid_t { 
#define P9_NOFID	(u32)(~0)

#define P9_MAXWELEM	16



/* Minimal header size: size[4] type[1] tag[2] */

#define P9_HDRSZ	7



/* ample room for Twrite/Rread header */

#define P9_IOHDRSZ	24
@@ -558,6 +561,7 @@ struct p9_fcall { 
	size_t offset;

	size_t capacity;



	struct kmem_cache *cache;

	u8 *sdata;

};

include/net/9p/client.h

+1 −0
Original line number Diff line number Diff line
@@ -123,6 +123,7 @@ struct p9_client { 
	struct p9_trans_module *trans_mod;

	enum p9_trans_status status;

	void *trans;

	struct kmem_cache *fcall_cache;



	union {

		struct {

net/9p/client.c

+32 −5
Original line number Diff line number Diff line
@@ -231,9 +231,16 @@ free_and_return: 
	return ret;

}



static int p9_fcall_init(struct p9_fcall *fc, int alloc_msize)

static int p9_fcall_init(struct p9_client *c, struct p9_fcall *fc,

			 int alloc_msize)

{

	if (likely(c->fcall_cache) && alloc_msize == c->msize) {

		fc->sdata = kmem_cache_alloc(c->fcall_cache, GFP_NOFS);

		fc->cache = c->fcall_cache;

	} else {

		fc->sdata = kmalloc(alloc_msize, GFP_NOFS);

		fc->cache = NULL;

	}

	if (!fc->sdata)

		return -ENOMEM;

	fc->capacity = alloc_msize;
@@ -242,6 +249,15 @@ static int p9_fcall_init(struct p9_fcall *fc, int alloc_msize) 


void p9_fcall_fini(struct p9_fcall *fc)

{

	/* sdata can be NULL for interrupted requests in trans_rdma,

	 * and kmem_cache_free does not do NULL-check for us

	 */

	if (unlikely(!fc->sdata))

		return;



	if (fc->cache)

		kmem_cache_free(fc->cache, fc->sdata);

	else

		kfree(fc->sdata);

}

EXPORT_SYMBOL(p9_fcall_fini);
@@ -267,9 +283,9 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size) 
	if (!req)

		return NULL;



	if (p9_fcall_init(&req->tc, alloc_msize))

	if (p9_fcall_init(c, &req->tc, alloc_msize))

		goto free_req;

	if (p9_fcall_init(&req->rc, alloc_msize))

	if (p9_fcall_init(c, &req->rc, alloc_msize))

		goto free;



	p9pdu_reset(&req->tc);
@@ -951,6 +967,7 @@ struct p9_client *p9_client_create(const char *dev_name, char *options) 


	clnt->trans_mod = NULL;

	clnt->trans = NULL;

	clnt->fcall_cache = NULL;



	client_id = utsname()->nodename;

	memcpy(clnt->name, client_id, strlen(client_id) + 1);
@@ -987,6 +1004,15 @@ struct p9_client *p9_client_create(const char *dev_name, char *options) 
	if (err)

		goto close_trans;



	/* P9_HDRSZ + 4 is the smallest packet header we can have that is

	 * followed by data accessed from userspace by read

	 */

	clnt->fcall_cache =

		kmem_cache_create_usercopy("9p-fcall-cache", clnt->msize,

					   0, 0, P9_HDRSZ + 4,

					   clnt->msize - (P9_HDRSZ + 4),

					   NULL);



	return clnt;



close_trans:
@@ -1018,6 +1044,7 @@ void p9_client_destroy(struct p9_client *clnt) 


	p9_tag_cleanup(clnt);



	kmem_cache_destroy(clnt->fcall_cache);

	kfree(clnt);

}

EXPORT_SYMBOL(p9_client_destroy);

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