[PATCH 4.19 10/72] 9p: add a per-client fcall kmem_cache

Greg Kroah-Hartman
2019-07-02T08:15:07Z

[ Upstream commit 91a76be37ff89795526c452a6799576b03bec501 ]

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: Dominique Martinet <dominique.martinet@cea.fr>
Acked-by: Jun Piao <piaojun@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Greg Kurz <groug@kaod.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/9p/9p.h | 4 ++++
include/net/9p/client.h | 1 +
net/9p/client.c | 37 ++++++++++++++++++++++++++++++++-----
3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/include/net/9p/9p.h b/include/net/9p/9p.h
index b8eb51a661e5..4ab293f574e0 100644
--- a/include/net/9p/9p.h
+++ b/include/net/9p/9p.h
@@ -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;
};

diff --git a/include/net/9p/client.h b/include/net/9p/client.h
index c2671d40bb6b..735f3979d559 100644
--- a/include/net/9p/client.h
+++ b/include/net/9p/client.h
@@ -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 {
diff --git a/net/9p/client.c b/net/9p/client.c
index 83e39fef58e1..7ef54719c6f7 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -237,9 +237,16 @@ static int parse_opts(char *opts, struct p9_client *clnt)
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)
{
- fc->sdata = kmalloc(alloc_msize, GFP_NOFS);
+ 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;
@@ -248,7 +255,16 @@ static int p9_fcall_init(struct p9_fcall *fc, int alloc_msize)

void p9_fcall_fini(struct p9_fcall *fc)
{
- kfree(fc->sdata);
+ /* 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);

@@ -273,9 +289,9 @@ 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);
@@ -965,6 +981,7 @@ 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);
@@ -1008,6 +1025,15 @@ 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:
@@ -1039,6 +1065,7 @@ 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);
--
2.20.1