This keeps consistent reads but defers writes to a half-second timer by implementing the suggested TODO in block/vvfat.c.
I noticed slow boot performance when testing a UKI image. It was roughly 18 seconds to a login prompt with a simple userspace. I profiled quickly with Sysprof which showed an overwhelming amount of time spent in check_directory_consistency(). The -drive in question here is the following: file=fat:rw:/tmp/machines-uki-esp-HVCXP3,format=raw,media=disk which has a temporary NvVars in it for quick throwaway VM testing which I use in conjunction with mkosi. With this commit in place, boot to login reduces from 18 seconds to 6. Signed-off-by: Christian Hergert <[email protected]> --- block/vvfat.c | 130 ++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 125 insertions(+), 5 deletions(-) diff --git a/block/vvfat.c b/block/vvfat.c index e334b9febb..49756ac5e0 100644 --- a/block/vvfat.c +++ b/block/vvfat.c @@ -32,6 +32,7 @@ #include "block/qdict.h" #include "qemu/module.h" #include "qemu/option.h" +#include "qemu/timer.h" #include "qemu/bswap.h" #include "migration/blocker.h" #include "qobject/qdict.h" @@ -53,8 +54,6 @@ Note that DOS assumes the system files to be the first files in the file system (test if the boot sector still relies on that fact)! */ /* MAYBE TODO: write block-visofs.c */ -/* TODO: call try_commit() only after a timeout */ - /* #define DEBUG */ #ifdef DEBUG @@ -80,6 +79,8 @@ static void checkpoint(void); #define DIR_KANJI_FAKE 0x05 #define DIR_FREE 0x00 +#define VVFAT_COMMIT_DELAY_NS (NANOSECONDS_PER_SECOND / 2) + /* dynamic array functions */ typedef struct array_t { char* pointer; @@ -332,6 +333,8 @@ typedef struct BDRVVVFATState { void* fat2; char* used_clusters; array_t commits; + QEMUTimer *commit_timer; + bool commit_pending; const char* path; int downcase_short_names; @@ -1052,6 +1055,8 @@ static BDRVVVFATState *vvv = NULL; static int enable_write_target(BlockDriverState *bs, Error **errp); static int coroutine_fn is_consistent(BDRVVVFATState *s); +static void vvfat_attach_aio_context(BlockDriverState *bs, + AioContext *new_context); static QemuOptsList runtime_opts = { .name = "vvfat", @@ -1278,6 +1283,7 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags, } qemu_co_mutex_init(&s->lock); + vvfat_attach_aio_context(bs, bdrv_get_aio_context(bs)); qemu_opts_del(opts); @@ -2973,6 +2979,60 @@ DLOG(checkpoint()); return do_commit(s); } +static int coroutine_fn GRAPH_RDLOCK +vvfat_commit_now(BDRVVVFATState *s) +{ + int ret; + + if (s->commit_timer) { + timer_del(s->commit_timer); + } + if (!s->commit_pending) { + return 0; + } + + qemu_co_mutex_lock(&s->lock); + ret = try_commit(s); + qemu_co_mutex_unlock(&s->lock); + + if (ret == 0) { + s->commit_pending = false; + } + + return ret; +} + +static void coroutine_fn vvfat_commit_timer_entry(void *opaque) +{ + BlockDriverState *bs = opaque; + BDRVVVFATState *s = bs->opaque; + GRAPH_RDLOCK_GUARD(); + + vvfat_commit_now(s); + bdrv_dec_in_flight(bs); +} + +static void vvfat_commit_timer_cb(void *opaque) +{ + BlockDriverState *bs = opaque; + Coroutine *co; + + co = qemu_coroutine_create(vvfat_commit_timer_entry, bs); + bdrv_inc_in_flight(bs); + qemu_coroutine_enter(co); +} + +static void vvfat_schedule_commit(BDRVVVFATState *s) +{ + s->commit_pending = true; + + if (s->commit_timer) { + timer_mod_ns(s->commit_timer, + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + + VVFAT_COMMIT_DELAY_NS); + } +} + static int coroutine_fn GRAPH_RDLOCK vvfat_write(BlockDriverState *bs, int64_t sector_num, const uint8_t *buf, int nb_sectors) @@ -3098,8 +3158,7 @@ DLOG(fprintf(stderr, "Write to qcow backend: %d + %d\n", (int)sector_num, nb_sec } DLOG(checkpoint()); - /* TODO: add timeout */ - try_commit(s); + vvfat_schedule_commit(s); DLOG(checkpoint()); return 0; @@ -3133,6 +3192,34 @@ vvfat_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes, return ret; } +static int coroutine_fn GRAPH_RDLOCK +vvfat_co_flush(BlockDriverState *bs) +{ + BDRVVVFATState *s = bs->opaque; + + if (s->qcow == NULL) { + return 0; + } + + return vvfat_commit_now(s); +} + +static void vvfat_drain_begin(BlockDriverState *bs) +{ + BDRVVVFATState *s = bs->opaque; + Coroutine *co; + + if (!s->commit_timer || !timer_pending(s->commit_timer)) { + return; + } + + timer_del(s->commit_timer); + + co = qemu_coroutine_create(vvfat_commit_timer_entry, bs); + bdrv_inc_in_flight(bs); + aio_co_enter(bdrv_get_aio_context(bs), co); +} + static int coroutine_fn vvfat_co_block_status(BlockDriverState *bs, unsigned int mode, int64_t offset, int64_t bytes, @@ -3229,6 +3316,11 @@ static void vvfat_close(BlockDriverState *bs) { BDRVVVFATState *s = bs->opaque; + if (s->commit_timer) { + timer_free(s->commit_timer); + s->commit_timer = NULL; + } + vvfat_close_current_file(s); array_free(&(s->fat)); array_free(&(s->directory)); @@ -3240,6 +3332,30 @@ static void vvfat_close(BlockDriverState *bs) } } +static void vvfat_detach_aio_context(BlockDriverState *bs) +{ + BDRVVVFATState *s = bs->opaque; + + if (s->commit_timer) { + timer_free(s->commit_timer); + s->commit_timer = NULL; + } +} + +static void vvfat_attach_aio_context(BlockDriverState *bs, + AioContext *new_context) +{ + BDRVVVFATState *s = bs->opaque; + + if (s->qcow) { + s->commit_timer = aio_timer_new(new_context, QEMU_CLOCK_VIRTUAL, + SCALE_NS, vvfat_commit_timer_cb, bs); + if (s->commit_pending) { + vvfat_schedule_commit(s); + } + } +} + static const char *const vvfat_strong_runtime_opts[] = { "dir", "fat-type", @@ -3263,7 +3379,11 @@ static BlockDriver bdrv_vvfat = { .bdrv_co_preadv = vvfat_co_preadv, .bdrv_co_pwritev = vvfat_co_pwritev, - .bdrv_co_block_status = vvfat_co_block_status, + .bdrv_co_flush = vvfat_co_flush, + .bdrv_drain_begin = vvfat_drain_begin, + .bdrv_co_block_status = vvfat_co_block_status, + .bdrv_detach_aio_context = vvfat_detach_aio_context, + .bdrv_attach_aio_context = vvfat_attach_aio_context, .strong_runtime_opts = vvfat_strong_runtime_opts, }; -- 2.54.0
