[PULL for-9.0 0/1] Block patches

[PULL for-9.0 0/1] Block patches

[Stefan Hajnoczi]

The following changes since commit fea445e8fe9acea4f775a832815ee22bdf2b0222:

  Merge tag 'pull-maintainer-final-for-real-this-time-200324-1' of https://gitlab.com/stsquad/qemu into staging (2024-03-21 10:31:56 +0000)

are available in the Git repository at:

  https://gitlab.com/stefanha/qemu.git tags/block-pull-request

for you to fetch changes up to 9352f80cd926fe2dde7c89b93ee33bb0356ff40e:

  coroutine: reserve 5,000 mappings (2024-03-21 13:14:30 -0400)

----------------------------------------------------------------
Pull request

I was too quick in sending the coroutine pool sizing change for -rc0 and still
needed to address feedback from Daniel Berrangé.

----------------------------------------------------------------

Stefan Hajnoczi (1):
  coroutine: reserve 5,000 mappings

 util/qemu-coroutine.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

-- 
2.44.0

[PULL for-9.0 1/1] coroutine: reserve 5,000 mappings

[Stefan Hajnoczi]

Daniel P. Berrangé <berrange@redhat.com> pointed out that the coroutine
pool size heuristic is very conservative. Instead of halving
max_map_count, he suggested reserving 5,000 mappings for non-coroutine
users based on observations of guests he has access to.

Fixes: 86a637e48104 ("coroutine: cap per-thread local pool size")
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20240320181232.1464819-1-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 util/qemu-coroutine.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c
index 2790959eaf..eb4eebefdf 100644
--- a/util/qemu-coroutine.c
+++ b/util/qemu-coroutine.c
@@ -377,12 +377,17 @@ static unsigned int get_global_pool_hard_max_size(void)
                             NULL) &&
         qemu_strtoi(contents, NULL, 10, &max_map_count) == 0) {
         /*
-         * This is a conservative upper bound that avoids exceeding
-         * max_map_count. Leave half for non-coroutine users like library
-         * dependencies, vhost-user, etc. Each coroutine takes up 2 VMAs so
-         * halve the amount again.
+         * This is an upper bound that avoids exceeding max_map_count. Leave a
+         * fixed amount for non-coroutine users like library dependencies,
+         * vhost-user, etc. Each coroutine takes up 2 VMAs so halve the
+         * remaining amount.
          */
-        return max_map_count / 4;
+        if (max_map_count > 5000) {
+            return (max_map_count - 5000) / 2;
+        } else {
+            /* Disable the global pool but threads still have local pools */
+            return 0;
+        }
     }
 #endif
 
-- 
2.44.0

Re: [PULL for-9.0 0/1] Block patches

[Peter Maydell]

On Thu, 21 Mar 2024 at 17:23, Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> The following changes since commit fea445e8fe9acea4f775a832815ee22bdf2b0222:
>
>   Merge tag 'pull-maintainer-final-for-real-this-time-200324-1' of https://gitlab.com/stsquad/qemu into staging (2024-03-21 10:31:56 +0000)
>
> are available in the Git repository at:
>
>   https://gitlab.com/stefanha/qemu.git tags/block-pull-request
>
> for you to fetch changes up to 9352f80cd926fe2dde7c89b93ee33bb0356ff40e:
>
>   coroutine: reserve 5,000 mappings (2024-03-21 13:14:30 -0400)
>
> ----------------------------------------------------------------
> Pull request
>
> I was too quick in sending the coroutine pool sizing change for -rc0 and still
> needed to address feedback from Daniel Berrangé.
>


Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/9.0
for any user-visible changes.

-- PMM