From 684b413b5483f57c890c171b9400076a0143b918 Mon Sep 17 00:00:00 2001 From: Niklas Cassel Date: Fri, 18 Sep 2026 16:06:42 +0200 Subject: virtio_blk: set the zone write granularity virtblk_read_zoned_limits() reads the write granularity that the device reports in virtio_blk_zoned_characteristics and assigns it to the physical block size and to io_min, but never to the limit that is named after it. queue_limits.zone_write_granularity is left at zero, so blk_validate_zoned_limits() raises it to the logical block size: if (lim->zone_write_granularity < lim->logical_block_size) lim->zone_write_granularity = lim->logical_block_size; A device that reports a granularity coarser than its logical block size, which is what the field exists to express, therefore has it silently reduced. A 512e host managed disk passed through to a guest reports a logical block size of 512 and a write granularity of 4096, and the guest ends up with a zone write granularity of 512. bio_split_alignment() returns lim->zone_write_granularity if it is non-zero and bio_split_io_at() may split a bio with as per bio_split_alignment(). This can real to the write getting rejected by the host drive, as the write is not aligned to the physical block size. zonefs also takes its block size from bdev_zone_write_granularity(), so it would incorrectly use 512 on a disk that requires 4096. sd_zbc_read_zones() sets the limit from the physical block size for the same reason. NVMe ZNS and null_blk leave it unset, but the fallback gives the right answer for them, as their write granularity is the logical block size. virtio carries a separate value that may exceed it. Set the zone write granularity from the value that the device reports. Fixes: 95bfec41bd3d ("virtio-blk: add support for zoned block devices") Signed-off-by: Niklas Cassel Reviewed-by: Stefan Hajnoczi Link: https://patch.msgid.link/20260918140641.2031075-2-cassel@kernel.org Signed-off-by: Jens Axboe --- lib/test_workqueue.c | 294 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 294 insertions(+) create mode 100644 lib/test_workqueue.c (limited to 'lib/test_workqueue.c') diff --git a/lib/test_workqueue.c b/lib/test_workqueue.c new file mode 100644 index 000000000..99e160bd5 --- /dev/null +++ b/lib/test_workqueue.c @@ -0,0 +1,294 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * Test module for stress and performance analysis of workqueue. + * + * Benchmarks queue_work() throughput on an unbound workqueue to measure + * pool->lock contention under different affinity scope configurations + * (e.g., cache vs cache_shard). + * + * The affinity scope is changed between runs via the workqueue's sysfs + * affinity_scope attribute (WQ_SYSFS). + * + * Copyright (c) 2026 Meta Platforms, Inc. and affiliates + * Copyright (c) 2026 Breno Leitao + * + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define WQ_NAME "bench_wq" +#define SCOPE_PATH "/sys/bus/workqueue/devices/" WQ_NAME "/affinity_scope" + +static int nr_threads; +module_param(nr_threads, int, 0444); +MODULE_PARM_DESC(nr_threads, + "Number of threads to spawn (default: 0 = num_online_cpus())"); + +static int wq_items = 50000; +module_param(wq_items, int, 0444); +MODULE_PARM_DESC(wq_items, + "Number of work items each thread queues (default: 50000)"); + +static struct workqueue_struct *bench_wq; +static atomic_t threads_done; +static DECLARE_COMPLETION(start_comp); +static DECLARE_COMPLETION(all_done_comp); + +struct thread_ctx { + struct completion work_done; + struct work_struct work; + u64 *latencies; + int cpu; + int items; +}; + +static void bench_work_fn(struct work_struct *work) +{ + struct thread_ctx *ctx = container_of(work, struct thread_ctx, work); + + complete(&ctx->work_done); +} + +static int bench_kthread_fn(void *data) +{ + struct thread_ctx *ctx = data; + ktime_t t_start, t_end; + int i; + + /* Wait for all threads to be ready */ + wait_for_completion(&start_comp); + + if (kthread_should_stop()) + return 0; + + for (i = 0; i < ctx->items; i++) { + reinit_completion(&ctx->work_done); + INIT_WORK(&ctx->work, bench_work_fn); + + t_start = ktime_get(); + queue_work(bench_wq, &ctx->work); + t_end = ktime_get(); + + ctx->latencies[i] = ktime_to_ns(ktime_sub(t_end, t_start)); + wait_for_completion(&ctx->work_done); + } + + if (atomic_dec_and_test(&threads_done)) + complete(&all_done_comp); + + /* + * Wait for kthread_stop() so the module text isn't freed + * while we're still executing. + */ + while (!kthread_should_stop()) + schedule(); + + return 0; +} + +static int cmp_u64(const void *a, const void *b) +{ + u64 va = *(const u64 *)a; + u64 vb = *(const u64 *)b; + + if (va < vb) + return -1; + if (va > vb) + return 1; + return 0; +} + +static int __init set_affn_scope(const char *scope) +{ + struct file *f; + loff_t pos = 0; + ssize_t ret; + + f = filp_open(SCOPE_PATH, O_WRONLY, 0); + if (IS_ERR(f)) { + pr_err("test_workqueue: open %s failed: %ld\n", + SCOPE_PATH, PTR_ERR(f)); + return PTR_ERR(f); + } + + ret = kernel_write(f, scope, strlen(scope), &pos); + filp_close(f, NULL); + + if (ret < 0) { + pr_err("test_workqueue: write '%s' failed: %zd\n", scope, ret); + return ret; + } + + return 0; +} + +static int __init run_bench(int n_threads, const char *scope, const char *label) +{ + struct task_struct **tasks; + unsigned long total_items; + struct thread_ctx *ctxs; + u64 *all_latencies; + ktime_t start, end; + int cpu, i, j, ret; + s64 elapsed_us; + + ret = set_affn_scope(scope); + if (ret) + return ret; + + ctxs = kcalloc(n_threads, sizeof(*ctxs), GFP_KERNEL); + if (!ctxs) + return -ENOMEM; + + tasks = kcalloc(n_threads, sizeof(*tasks), GFP_KERNEL); + if (!tasks) { + kfree(ctxs); + return -ENOMEM; + } + + total_items = (unsigned long)n_threads * wq_items; + all_latencies = kvmalloc_array(total_items, sizeof(u64), GFP_KERNEL); + if (!all_latencies) { + kfree(tasks); + kfree(ctxs); + return -ENOMEM; + } + + /* Allocate per-thread latency arrays */ + for (i = 0; i < n_threads; i++) { + ctxs[i].latencies = kvmalloc_array(wq_items, sizeof(u64), + GFP_KERNEL); + if (!ctxs[i].latencies) { + while (--i >= 0) + kvfree(ctxs[i].latencies); + kvfree(all_latencies); + kfree(tasks); + kfree(ctxs); + return -ENOMEM; + } + } + + atomic_set(&threads_done, n_threads); + reinit_completion(&all_done_comp); + reinit_completion(&start_comp); + + /* Create kthreads, each bound to a different online CPU */ + i = 0; + for_each_online_cpu(cpu) { + if (i >= n_threads) + break; + + ctxs[i].cpu = cpu; + ctxs[i].items = wq_items; + init_completion(&ctxs[i].work_done); + + tasks[i] = kthread_create(bench_kthread_fn, &ctxs[i], + "wq_bench/%d", cpu); + if (IS_ERR(tasks[i])) { + ret = PTR_ERR(tasks[i]); + pr_err("test_workqueue: failed to create kthread %d: %d\n", + i, ret); + /* Unblock threads waiting on start_comp before stopping them */ + complete_all(&start_comp); + while (--i >= 0) + kthread_stop(tasks[i]); + goto out_free; + } + + kthread_bind(tasks[i], cpu); + wake_up_process(tasks[i]); + i++; + } + + /* Start timing and release all threads */ + start = ktime_get(); + complete_all(&start_comp); + + /* Wait for all threads to finish the benchmark */ + wait_for_completion(&all_done_comp); + + /* Drain any remaining work */ + flush_workqueue(bench_wq); + + /* Ensure all kthreads have fully exited before module memory is freed */ + for (i = 0; i < n_threads; i++) + kthread_stop(tasks[i]); + + end = ktime_get(); + elapsed_us = ktime_us_delta(end, start); + + /* Merge all per-thread latencies and sort for percentile calculation */ + j = 0; + for (i = 0; i < n_threads; i++) { + memcpy(&all_latencies[j], ctxs[i].latencies, + wq_items * sizeof(u64)); + j += wq_items; + } + + sort(all_latencies, total_items, sizeof(u64), cmp_u64, NULL); + + pr_info("test_workqueue: %-16s %llu items/sec\tp50=%llu\tp90=%llu\tp95=%llu ns\n", + label, + elapsed_us ? div_u64(total_items * 1000000ULL, elapsed_us) : 0, + all_latencies[total_items * 50 / 100], + all_latencies[total_items * 90 / 100], + all_latencies[total_items * 95 / 100]); + + ret = 0; +out_free: + for (i = 0; i < n_threads; i++) + kvfree(ctxs[i].latencies); + kvfree(all_latencies); + kfree(tasks); + kfree(ctxs); + + return ret; +} + +static const char * const bench_scopes[] = { + "cpu", "smt", "cache_shard", "cache", "numa", "system", +}; + +static int __init test_workqueue_init(void) +{ + int n_threads = min(nr_threads ?: num_online_cpus(), num_online_cpus()); + int i; + + if (wq_items <= 0) { + pr_err("test_workqueue: wq_items must be > 0\n"); + return -EINVAL; + } + + bench_wq = alloc_workqueue(WQ_NAME, WQ_UNBOUND | WQ_SYSFS, 0); + if (!bench_wq) + return -ENOMEM; + + pr_info("test_workqueue: running %d threads, %d items/thread\n", + n_threads, wq_items); + + for (i = 0; i < ARRAY_SIZE(bench_scopes); i++) + run_bench(n_threads, bench_scopes[i], bench_scopes[i]); + + destroy_workqueue(bench_wq); + + /* Return -EAGAIN so the module doesn't stay loaded after the benchmark */ + return -EAGAIN; +} + +module_init(test_workqueue_init); +MODULE_AUTHOR("Breno Leitao "); +MODULE_DESCRIPTION("Stress/performance benchmark for workqueue subsystem"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1