Commit 0ea9629a authored by Tomasz Zawadzki's avatar Tomasz Zawadzki
Browse files

app/spdk_dd: unaffinitize SQ_POLL thread 



Turns out that kernel SQ_POLL thread inherits the same
CPU mask as the thread it was called from. In case of SPDK
that would cover the CPU mask of the application.
This severely limits the throughput, as SPDK and kernel
thread compete for the same core. To the order of less than
1 MiB/s, resulting in test time outs on CI too.

There does not seem to be a way to remove this restriction.
Meanwhile IORING_SETUP_SQ_AFF during ring initialization
only allows to pass a specific core, rather than a mask.

IORING_REGISTER_IOWQ_AFF opcode to io_uring_register() should
have been the solution to this problem, but it does not work
on my system as expected. Leaving unaffinitization as only
solution for now.

This patch unaffinitizes the SPDK thread only for
the ring initialization, so no such restriction is imposed
on the SQ_POLL thread.

Signed-off-by: default avatarTomasz Zawadzki <tomasz.zawadzki@intel.com>
Change-Id: I7146c5e08bcb63219f800a3e0c343bb09fabd9f8
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/21880


Community-CI: Mellanox Build Bot
Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarShuhei Matsumoto <smatsumoto@nvidia.com>
Reviewed-by: default avatarJim Harris <jim.harris@samsung.com>
parent e59cd10a

app/spdk_dd/spdk_dd.c

+23 −6
Original line number Diff line number Diff line
@@ -1006,6 +1006,20 @@ dd_is_blk(int fd) 
	return S_ISBLK(st.st_mode);

}



struct dd_uring_init_ctx {

	unsigned int io_uring_flags;

	int rc;

};



static void *

dd_uring_init(void *arg)

{

	struct dd_uring_init_ctx *ctx = arg;



	ctx->rc = io_uring_queue_init(g_opts.queue_depth * 2, &g_job.u.uring.ring, ctx->io_uring_flags);

	return ctx;

}



static int

dd_register_files(void)

{
@@ -1176,20 +1190,23 @@ dd_run(void *arg1) 
	if (g_opts.input_file || g_opts.output_file) {

#ifdef SPDK_CONFIG_URING

		if (g_opts.aio == false) {

			unsigned int io_uring_flags = IORING_SETUP_SQPOLL;

			struct dd_uring_init_ctx ctx;

			int flags = parse_flags(g_opts.input_file_flags) & parse_flags(g_opts.output_file_flags);



			ctx.io_uring_flags = IORING_SETUP_SQPOLL;

			if ((flags & O_DIRECT) != 0 &&

			    dd_is_blk(g_job.input.u.uring.fd) &&

			    dd_is_blk(g_job.output.u.uring.fd)) {

				io_uring_flags = IORING_SETUP_IOPOLL;

				ctx.io_uring_flags = IORING_SETUP_IOPOLL;

			}



			g_job.u.uring.poller = SPDK_POLLER_REGISTER(dd_uring_poll, NULL, 0);

			rc = io_uring_queue_init(g_opts.queue_depth * 2, &g_job.u.uring.ring, io_uring_flags);

			if (rc) {

				SPDK_ERRLOG("Failed to create io_uring: %d (%s)\n", rc, spdk_strerror(-rc));

				dd_exit(rc);



			/* Initialized uring kernel threads inherit parent process CPU mask, to avoid conflicting

			 * with SPDK cores initialize uring without any affinity. */

			if (spdk_call_unaffinitized(dd_uring_init, &ctx) == NULL || ctx.rc) {

				SPDK_ERRLOG("Failed to create io_uring: %d (%s)\n", ctx.rc, spdk_strerror(-ctx.rc));

				dd_exit(ctx.rc);

				return;

			}

			g_job.u.uring.active = true;