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Re: [PATCH v2 2/4] util/defer-call: move defer_call() to util/
From: |
Stefan Hajnoczi |
Subject: |
Re: [PATCH v2 2/4] util/defer-call: move defer_call() to util/ |
Date: |
Wed, 13 Sep 2023 15:39:52 -0400 |
On Fri, Aug 18, 2023 at 10:31:40AM +0200, Philippe Mathieu-Daudé wrote:
> Hi Stefan,
>
> On 17/8/23 17:58, Stefan Hajnoczi wrote:
> > The networking subsystem may wish to use defer_call(), so move the code
> > to util/ where it can be reused.
> >
> > As a reminder of what defer_call() does:
> >
> > This API defers a function call within a defer_call_begin()/defer_call_end()
> > section, allowing multiple calls to batch up. This is a performance
> > optimization that is used in the block layer to submit several I/O requests
> > at once instead of individually:
> >
> > defer_call_begin(); <-- start of section
> > ...
> > defer_call(my_func, my_obj); <-- deferred my_func(my_obj) call
> > defer_call(my_func, my_obj); <-- another
> > defer_call(my_func, my_obj); <-- another
> > ...
> > defer_call_end(); <-- end of section, my_func(my_obj) is called once
> >
> > Suggested-by: Ilya Maximets <i.maximets@ovn.org>
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> > MAINTAINERS | 3 ++-
> > include/qemu/defer-call.h | 15 +++++++++++++++
> > include/sysemu/block-backend-io.h | 4 ----
> > block/blkio.c | 1 +
> > block/io_uring.c | 1 +
> > block/linux-aio.c | 1 +
> > block/nvme.c | 1 +
> > hw/block/dataplane/xen-block.c | 1 +
> > hw/block/virtio-blk.c | 1 +
> > hw/scsi/virtio-scsi.c | 1 +
> > block/plug.c => util/defer-call.c | 2 +-
> > block/meson.build | 1 -
> > util/meson.build | 1 +
> > 13 files changed, 26 insertions(+), 7 deletions(-)
> > create mode 100644 include/qemu/defer-call.h
> > rename block/plug.c => util/defer-call.c (99%)
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 6111b6b4d9..7cd7132ffc 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -2676,12 +2676,13 @@ S: Supported
> > F: util/async.c
> > F: util/aio-*.c
> > F: util/aio-*.h
> > +F: util/defer-call.c
>
> If used by network/other backends, maybe worth adding a
> brand new section instead, rather than "Block I/O path".
Changes to defer-call.c will go through my block tree. We don't split
out the event loop (async.c, aio-*.c, etc) either even though it's
shared by other subsystems. The important thing is that
scripts/get_maintainer.pl identifies the maintainers.
I'd rather not create lots of micro-subsystems in MAINTAINERS that
duplicate my email and block git repo URL.
>
> > F: util/fdmon-*.c
> > F: block/io.c
> > -F: block/plug.c
> > F: migration/block*
> > F: include/block/aio.h
> > F: include/block/aio-wait.h
> > +F: include/qemu/defer-call.h
> > F: scripts/qemugdb/aio.py
> > F: tests/unit/test-fdmon-epoll.c
> > T: git https://github.com/stefanha/qemu.git block
> > diff --git a/include/qemu/defer-call.h b/include/qemu/defer-call.h
> > new file mode 100644
> > index 0000000000..291f86c987
> > --- /dev/null
> > +++ b/include/qemu/defer-call.h
> > @@ -0,0 +1,15 @@
> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> > +/*
> > + * Deferred calls
> > + *
> > + * Copyright Red Hat.
> > + */
> > +
> > +#ifndef QEMU_DEFER_CALL_H
> > +#define QEMU_DEFER_CALL_H
> > +
>
> Please add smth like:
>
> /* See documentation in util/defer-call.c */
Sure, will fix.
>
> > +void defer_call_begin(void);
> > +void defer_call_end(void);
> > +void defer_call(void (*fn)(void *), void *opaque);
> > +
> > +#endif /* QEMU_DEFER_CALL_H */
>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>
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