Re: [PATCH v3 15/21] fuse: Process requests in coroutines

[Kevin Wolf <kwolf@redhat.com>]

Am 01.07.2025 um 13:44 hat Hanna Czenczek geschrieben:
> Make fuse_process_request() a coroutine_fn (fuse_co_process_request())
> and have read_from_fuse_fd() launch it inside of a newly created
> coroutine instead of running it synchronously.  This way, we can process
> requests in parallel.
> 
> These are the benchmark results, compared to (a) the original results
> with libfuse, and (b) the results after switching away from libfuse
> (i.e. before this patch):
> 
> file:                  (vs. libfuse / vs. no libfuse)
>   read:
>     seq aio:   120.6k ±1.1k (+ 53 % / + 58 %)
>     rand aio:  113.3k ±5.9k (+188 % / +325 %)
>     seq sync:   52.4k ±0.4k (+ 61 % / + 10 %)
>     rand sync:  10.4k ±0.4k (+  6 % / +  3 %)
>   write:
>     seq aio:    79.8k ±0.8k (+ 29 % / + 37 %)
>     rand aio:   79.0k ±0.6k (+ 29 % / + 36 %)
>     seq sync:   41.5k ±0.3k (+ 49 % / + 15 %)
>     rand sync:  41.4k ±0.2k (+ 50 % / + 15 %)
> null:
>   read:
>     seq aio:   266.1k ±1.5k (+ 24 % / -  1 %)
>     rand aio:  264.1k ±2.5k (+ 24 % / ±  0 %)
>     seq sync:  135.6k ±3.2k (+ 50 % / +  1 %)
>     rand sync: 134.7k ±3.0k (+ 50 % / +  2 %)
>   write:
>     seq aio:   281.0k ±1.8k (+ 38 % / +  2 %)
>     rand aio:  288.1k ±6.1k (+ 43 % / +  6 %)
>     seq sync:  142.2k ±3.1k (+ 65 % / +  9 %)
>     rand sync: 141.1k ±2.9k (+ 66 % / + 11 %)
> 
> So for non-AIO cases (and the null driver, which does not yield), there
> is little change; but for file AIO, results greatly improve, resolving
> the performance issue we saw before (when switching away from libfuse).
> 
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
> ---
>  block/export/fuse.c | 194 ++++++++++++++++++++++++++------------------
>  1 file changed, 113 insertions(+), 81 deletions(-)
> 
> diff --git a/block/export/fuse.c b/block/export/fuse.c
> index 8ea590ba67..0648b5bc7d 100644
> --- a/block/export/fuse.c
> +++ b/block/export/fuse.c
> @@ -27,6 +27,7 @@
>  #include "block/qapi.h"
>  #include "qapi/error.h"
>  #include "qapi/qapi-commands-block.h"
> +#include "qemu/coroutine.h"
>  #include "qemu/error-report.h"
>  #include "qemu/main-loop.h"
>  #include "system/block-backend.h"
> @@ -86,6 +87,12 @@ typedef struct FuseExport {
>      gid_t st_gid;
>  } FuseExport;
>  
> +/* Parameters to the request processing coroutine */
> +typedef struct FuseRequestCoParam {
> +    FuseExport *exp;
> +    int got_request;
> +} FuseRequestCoParam;

This type is unused.

Kevin