| Message ID | 20240320181232.1464819-1-stefanha@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | coroutine: reserve 5,000 mappings | expand |
On Wed, Mar 20, 2024 at 02:12:32PM -0400, Stefan Hajnoczi wrote: > 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") It wasn't really broken, so "Tweaks" or "Enhances" rather than "Fixes" if you like :-) > 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 Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> With regards, Daniel
On Wed, Mar 20, 2024 at 02:12:32PM -0400, Stefan Hajnoczi wrote: > 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> > --- > util/qemu-coroutine.c | 15 ++++++++++----- > 1 file changed, 10 insertions(+), 5 deletions(-) Discussed with Kevin and applied to my block tree: https://gitlab.com/stefanha/qemu/commits/block Stefan
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
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> --- util/qemu-coroutine.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)