Re: [PATCH 2/2] tcg: use QTree instead of GTree

[Daniel P . Berrangé]

On Tue, Jan 10, 2023 at 10:55:36PM -0500, Emilio Cota wrote:
> qemu-user can hang in a multi-threaded fork. One common
> reason is that when creating a TB, between fork and exec
> we manipulate a GTree whose memory allocator (GSlice) is
> not fork-safe.
> 
> Although POSIX does not mandate it, the system's allocator
> (e.g. tcmalloc, libc malloc) is probably fork-safe.
> 
> Fix some of these hangs by using QTree, which uses
> the system's allocator.
> 
> For more details, see:
>   https://gitlab.com/qemu-project/qemu/-/issues/285
> 
> Performance impact on linux-user:
> - ~2% slowdown in spec06
> - 1.05% slowdown in Nbench-int
> - 4.51% slowdown in Nbench-fp

What do you get *before* applying this patch, if you just run
linux-user with G_SLICE=always-malloc set ?

Also what libc impl were you testing with ? glibc or musl or something
else ?

With regards,
Daniel
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