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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772007234; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=L83tmmVEdGQV/uGUec+kZ4/BaRD7oWY0T8JaJvvXus0=; b=TFFU/G+cHAhvqZs+43nCf8+kK4RFEPAcXhq3/tOjuXhVXldyQCimWaJxkZTlB9XpCIdBb5 gemDkss0n4njhD8aGHzBSc3tMz7gPksIkc5fE6GbjOIYCZMJ0SRnaRX+yl3ZhoY/f2Ztv3 yCPuXapzKZfvi1OeWGS2WDLplawH2Fw= X-MC-Unique: nPinB27OO16c3e1UBhRgvA-1 X-Mimecast-MFC-AGG-ID: nPinB27OO16c3e1UBhRgvA_1772007229 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , qemu-block@nongnu.org, Kevin Wolf , Fam Zheng , Jens Axboe Subject: [PATCH v2 2/4] aio-posix: enable IORING_SETUP_SINGLE_ISSUER Date: Wed, 25 Feb 2026 16:13:34 +0800 Message-ID: <20260225081336.1639325-3-stefanha@redhat.com> In-Reply-To: <20260225081336.1639325-1-stefanha@redhat.com> References: <20260225081336.1639325-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" IORING_SETUP_SINGLE_ISSUER enables optimizations in the host Linux kernel's io_uring code when the io_uring context is only used from a single thread. This is true is QEMU because io_uring SQEs are submitted from the same thread that processes the CQEs. Signed-off-by: Stefan Hajnoczi --- util/fdmon-io_uring.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/util/fdmon-io_uring.c b/util/fdmon-io_uring.c index d0b56127c6..ec056b4818 100644 --- a/util/fdmon-io_uring.c +++ b/util/fdmon-io_uring.c @@ -452,13 +452,31 @@ static const FDMonOps fdmon_io_uring_ops =3D { .add_sqe =3D fdmon_io_uring_add_sqe, }; =20 +static inline bool is_creating_iothread(void) +{ + return qemu_get_thread_id() !=3D getpid(); +} + bool fdmon_io_uring_setup(AioContext *ctx, Error **errp) { + unsigned flags =3D 0; int ret; =20 + /* + * The main thread's AioContexts are created from the main loop thread= but + * may be accessed from multiple threads (e.g. vCPUs or the migration + * thread). IOThread AioContexts are only accessed from the IOThread + * itself. + */ +#if IORING_SETUP_SINGLE_ISSUER + if (is_creating_iothread()) { + flags |=3D IORING_SETUP_SINGLE_ISSUER; + } +#endif + ctx->io_uring_fd_tag =3D NULL; =20 - ret =3D io_uring_queue_init(FDMON_IO_URING_ENTRIES, &ctx->fdmon_io_uri= ng, 0); + ret =3D io_uring_queue_init(FDMON_IO_URING_ENTRIES, &ctx->fdmon_io_uri= ng, flags); if (ret !=3D 0) { error_setg_errno(errp, -ret, "Failed to initialize io_uring"); return false; --=20 2.53.0