This decompressor can introduce a huge latency when a to be executed process have to read and decompress directly from mass storage. Using a QSPI flash and squashfs, starting htop causes a latency of ~8000µs to a running cyclictest. The "multiple decompressor" is fine though. The cause is that squashfs_decompress() calls get_cpu_ptr(). If this is done on all CPUs no task will be executed until the decompression has finished. Signed-off-by: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx> --- fs/squashfs/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig index 1adb3346b9d6..246c5966173d 100644 --- a/fs/squashfs/Kconfig +++ b/fs/squashfs/Kconfig @@ -86,6 +86,7 @@ config SQUASHFS_DECOMP_MULTI config SQUASHFS_DECOMP_MULTI_PERCPU bool "Use percpu multiple decompressors for parallel I/O" + depends on !PREEMPT_RT_BASE help By default Squashfs uses a single decompressor but it gives poor performance on parallel I/O workloads when using multiple CPU -- 2.16.1 -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
