diff options
| author | Ian Munsie | 2015-05-08 22:55:18 +1000 |
|---|---|---|
| committer | Michael Ellerman | 2015-06-03 13:27:15 +1000 |
| commit | 8ac75b96be71e20ec1785ca18170890c4dfffe87 (patch) | |
| tree | 8b06520ebf5859bf62fee63e53b2a0581728ec6e /drivers/misc | |
| parent | e36f6fe1f7aa4238478d4b253aac7d3fcfff6ee0 (diff) | |
cxl: Use call_rcu to reduce latency when releasing the afu fd
The afu fd release path was identified as a significant bottleneck in
the overall performance of cxl. While an optimal AFU design would
minimise the need to close & reopen the AFU fd, it is not always
practical to avoid.
The bottleneck seems to be down to the call to synchronize_rcu(), which
will block until every other thread is guaranteed to be out of an RCU
critical section. Replace it with call_rcu() to free the context
structures later so we can return to the application sooner.
This reduces the time spent in the fd release path from 13356 usec to
13.3 usec - about a 100x speed up.
Reported-by: Fei K Chen <uchen@cn.ibm.com>
Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'drivers/misc')
| -rw-r--r-- | drivers/misc/cxl/context.c | 15 | ||||
| -rw-r--r-- | drivers/misc/cxl/cxl.h | 2 |
2 files changed, 12 insertions, 5 deletions
diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c index d1b55fe62817..78ce990d77ca 100644 --- a/drivers/misc/cxl/context.c +++ b/drivers/misc/cxl/context.c @@ -232,12 +232,9 @@ void cxl_context_detach_all(struct cxl_afu *afu) mutex_unlock(&afu->contexts_lock); } -void cxl_context_free(struct cxl_context *ctx) +static void reclaim_ctx(struct rcu_head *rcu) { - mutex_lock(&ctx->afu->contexts_lock); - idr_remove(&ctx->afu->contexts_idr, ctx->pe); - mutex_unlock(&ctx->afu->contexts_lock); - synchronize_rcu(); + struct cxl_context *ctx = container_of(rcu, struct cxl_context, rcu); free_page((u64)ctx->sstp); ctx->sstp = NULL; @@ -245,3 +242,11 @@ void cxl_context_free(struct cxl_context *ctx) put_pid(ctx->pid); kfree(ctx); } + +void cxl_context_free(struct cxl_context *ctx) +{ + mutex_lock(&ctx->afu->contexts_lock); + idr_remove(&ctx->afu->contexts_idr, ctx->pe); + mutex_unlock(&ctx->afu->contexts_lock); + call_rcu(&ctx->rcu, reclaim_ctx); +} diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h index cfee819bf5d4..b361b48d1b01 100644 --- a/drivers/misc/cxl/cxl.h +++ b/drivers/misc/cxl/cxl.h @@ -457,6 +457,8 @@ struct cxl_context { bool pending_irq; bool pending_fault; bool pending_afu_err; + + struct rcu_head rcu; }; struct cxl { |