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Date: Tue, 31 Jul 2018 09:18:40 +0800
From: piaojun <piaojun@...wei.com>
To: Dominique Martinet <asmadeus@...ewreck.org>,
<v9fs-developer@...ts.sourceforge.net>
CC: <linux-fsdevel@...r.kernel.org>, Greg Kurz <groug@...d.org>,
"Matthew Wilcox" <willy@...radead.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [V9fs-developer] [PATCH 2/2] net/9p: add a per-client fcall
kmem_cache
Hi Dominique,
Could you help paste some test result before-and-after the patch applied?
And I have a little suggestion in comments below.
On 2018/7/30 17:34, Dominique Martinet wrote:
> From: Dominique Martinet <dominique.martinet@....fr>
>
> Having a specific cache for the fcall allocations helps speed up
> allocations a bit, especially in case of non-"round" msizes.
>
> 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.
>
> Signed-off-by: Dominique Martinet <dominique.martinet@....fr>
> ---
> include/net/9p/client.h | 2 ++
> net/9p/client.c | 40 ++++++++++++++++++++++++++++++++--------
> net/9p/trans_rdma.c | 2 +-
> 3 files changed, 35 insertions(+), 9 deletions(-)
>
> diff --git a/include/net/9p/client.h b/include/net/9p/client.h
> index 4b4ac1362ad5..8d9bc7402a42 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 {
> @@ -230,6 +231,7 @@ int p9_client_mkdir_dotl(struct p9_fid *fid, const char *name, int mode,
> kgid_t gid, struct p9_qid *);
> int p9_client_lock_dotl(struct p9_fid *fid, struct p9_flock *flock, u8 *status);
> int p9_client_getlock_dotl(struct p9_fid *fid, struct p9_getlock *fl);
> +void p9_fcall_free(struct p9_client *c, struct p9_fcall *fc);
> struct p9_req_t *p9_tag_lookup(struct p9_client *, u16);
> void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status);
>
> diff --git a/net/9p/client.c b/net/9p/client.c
> index ba99a94a12c9..215e3b1ed7b4 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -231,15 +231,34 @@ static int parse_opts(char *opts, struct p9_client *clnt)
> return ret;
> }
>
> -static int p9_fcall_alloc(struct p9_fcall *fc, int alloc_msize)
> +static int p9_fcall_alloc(struct p9_client *c, struct p9_fcall *fc,
> + int alloc_msize)
> {
> - fc->sdata = kmalloc(alloc_msize, GFP_NOFS);
> + if (c->fcall_cache && alloc_msize == c->msize)
> + fc->sdata = kmem_cache_alloc(c->fcall_cache, GFP_NOFS);
> + else
> + fc->sdata = kmalloc(alloc_msize, GFP_NOFS);
> if (!fc->sdata)
> return -ENOMEM;
> fc->capacity = alloc_msize;
> return 0;
> }
>
> +void p9_fcall_free(struct p9_client *c, 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 (c->fcall_cache && fc->capacity == c->msize)
> + kmem_cache_free(c->fcall_cache, fc->sdata);
> + else
> + kfree(fc->sdata);
> +}
> +EXPORT_SYMBOL(p9_fcall_free);
> +
> static struct kmem_cache *p9_req_cache;
>
> /**
> @@ -261,9 +280,9 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
> if (!req)
> return NULL;
>
> - if (p9_fcall_alloc(&req->tc, alloc_msize))
> + if (p9_fcall_alloc(c, &req->tc, alloc_msize))
> goto free;
> - if (p9_fcall_alloc(&req->rc, alloc_msize))
> + if (p9_fcall_alloc(c, &req->rc, alloc_msize))
> goto free;
>
> p9pdu_reset(&req->tc);
> @@ -288,8 +307,8 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size)
> return req;
>
> free:
> - kfree(req->tc.sdata);
> - kfree(req->rc.sdata);
> + p9_fcall_free(c, &req->tc);
> + p9_fcall_free(c, &req->rc);
> kmem_cache_free(p9_req_cache, req);
> return ERR_PTR(-ENOMEM);
> }
> @@ -333,8 +352,8 @@ static void p9_free_req(struct p9_client *c, struct p9_req_t *r)
> spin_lock_irqsave(&c->lock, flags);
> idr_remove(&c->reqs, tag);
> spin_unlock_irqrestore(&c->lock, flags);
> - kfree(r->tc.sdata);
> - kfree(r->rc.sdata);
> + p9_fcall_free(c, &r->tc);
> + p9_fcall_free(c, &r->rc);
> kmem_cache_free(p9_req_cache, r);
> }
>
> @@ -944,6 +963,7 @@ 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);
> @@ -980,6 +1000,9 @@ struct p9_client *p9_client_create(const char *dev_name, char *options)
> if (err)
> goto close_trans;
>
> + clnt->fcall_cache = kmem_cache_create("9p-fcall-cache", clnt->msize,
> + 0, 0, NULL);
> +
> return clnt;
>
> close_trans:
> @@ -1011,6 +1034,7 @@ void p9_client_destroy(struct p9_client *clnt)
>
> p9_tag_cleanup(clnt);
>
> + kmem_cache_destroy(clnt->fcall_cache);
We could set NULL for fcall_cache in case of use-after-free.
> kfree(clnt);
> }
> EXPORT_SYMBOL(p9_client_destroy);
> diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c
> index c5cac97df7f7..5e43f0a00b3a 100644
> --- a/net/9p/trans_rdma.c
> +++ b/net/9p/trans_rdma.c
> @@ -445,7 +445,7 @@ static int rdma_request(struct p9_client *client, struct p9_req_t *req)
> if (unlikely(atomic_read(&rdma->excess_rc) > 0)) {
> if ((atomic_sub_return(1, &rdma->excess_rc) >= 0)) {
> /* Got one! */
> - kfree(req->rc.sdata);
> + p9_fcall_free(client, &req->rc);
> req->rc.sdata = NULL;
> goto dont_need_post_recv;
> } else {
>
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