From 090bf5a0f40030f4ef294a3edb84c5e99b843c7f Mon Sep 17 00:00:00 2001 From: Xueqin Luo Date: Tue, 21 Oct 2025 19:37:27 +0800 Subject: [PATCH] PM: hibernate: make compression threads configurable MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The number of compression/decompression threads has a direct impact on hibernate image generation and resume latency. Using more threads can reduce overall resume time, but on systems with fewer CPU cores it may also introduce contention and reduce efficiency. Performance was evaluated on an 8-core ARM system, averaged over 10 runs: Threads Hibernate(s) Resume(s) -------------------------------- 3 12.14 18.86 4 12.28 17.48 5 11.09 16.77 6 11.08 16.44 With 5–6 threads, resume latency improves by approximately 12% compared to the default 3-thread configuration, with negligible impact on hibernate time. Introduce a new kernel parameter `hibernate_compression_threads=` that allows users and integrators to tune the number of compression/decompression threads at boot. This provides a way to balance performance and CPU utilization across a wide range of hardware without recompiling the kernel. Signed-off-by: Xueqin Luo Link: https://patch.msgid.link/f24b3ca6416e230a515a154ed4c121d72a7e05a6.1761046167.git.luoxueqin@kylinos.cn Signed-off-by: Rafael J. Wysocki --- .../admin-guide/kernel-parameters.txt | 10 ++++++++ kernel/power/swap.c | 25 ++++++++++++++++--- 2 files changed, 31 insertions(+), 4 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6c42061ca20e5..46db3cbb838f2 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1907,6 +1907,16 @@ /sys/power/pm_test). Only available when CONFIG_PM_DEBUG is set. Default value is 5. + hibernate_compression_threads= + [HIBERNATION] + Set the number of threads used for compressing or decompressing + hibernation images. + + Format: + Default: 3 + Minimum: 1 + Example: hibernate_compression_threads=4 + highmem=nn[KMG] [KNL,BOOT,EARLY] forces the highmem zone to have an exact size of . This works even on boxes that have no highmem otherwise. This also works to reduce highmem diff --git a/kernel/power/swap.c b/kernel/power/swap.c index f8c13f5672ec2..aa11576e92a97 100644 --- a/kernel/power/swap.c +++ b/kernel/power/swap.c @@ -519,8 +519,9 @@ static int swap_writer_finish(struct swap_map_handle *handle, CMP_HEADER, PAGE_SIZE) #define CMP_SIZE (CMP_PAGES * PAGE_SIZE) -/* Maximum number of threads for compression/decompression. */ -#define CMP_THREADS 3 +/* Default number of threads for compression/decompression. */ +#define CMP_THREADS 3 +static unsigned int hibernate_compression_threads = CMP_THREADS; /* Minimum/maximum number of pages for read buffering. */ #define CMP_MIN_RD_PAGES 1024 @@ -741,7 +742,7 @@ static int save_compressed_image(struct swap_map_handle *handle, * footprint. */ nr_threads = num_online_cpus() - 1; - nr_threads = clamp_val(nr_threads, 1, CMP_THREADS); + nr_threads = clamp_val(nr_threads, 1, hibernate_compression_threads); page = (void *)__get_free_page(GFP_NOIO | __GFP_HIGH); if (!page) { @@ -1257,7 +1258,7 @@ static int load_compressed_image(struct swap_map_handle *handle, * footprint. */ nr_threads = num_online_cpus() - 1; - nr_threads = clamp_val(nr_threads, 1, CMP_THREADS); + nr_threads = clamp_val(nr_threads, 1, hibernate_compression_threads); page = vmalloc_array(CMP_MAX_RD_PAGES, sizeof(*page)); if (!page) { @@ -1697,3 +1698,19 @@ static int __init swsusp_header_init(void) } core_initcall(swsusp_header_init); + +static int __init hibernate_compression_threads_setup(char *str) +{ + int rc = kstrtouint(str, 0, &hibernate_compression_threads); + + if (rc) + return rc; + + if (hibernate_compression_threads < 1) + hibernate_compression_threads = CMP_THREADS; + + return 1; + +} + +__setup("hibernate_compression_threads=", hibernate_compression_threads_setup); -- 2.47.3