From: Geunsik Lim <geunsik.lim@xxxxxxxxxxx> Support kbuild menu to select memory unmap operation size at build time. Signed-off-by: Geunsik Lim <geunsik.lim@xxxxxxxxxxx> Acked-by: Hyunjin Choi <hj89.choi@xxxxxxxxxxx> --- init/Kconfig | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ mm/memory.c | 21 +++++++++++----- 2 files changed, 84 insertions(+), 7 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 56240e7..0983961 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -557,6 +557,76 @@ config LOG_BUF_SHIFT 13 => 8 KB 12 => 4 KB +config PREEMPT_OK_MUNMAP_RANGE + int "Memory unmap unit on preemption mode (8 => 32KB)" + depends on !PREEMPT_NONE + range 8 2048 + default 8 + help + unmap_vmas(=unmap a range of memory covered by a list of vma) is treading + a delicate and uncomfortable line between hi-performance and low-latency. + We've chosen to improve performance at the expense of latency. + + So although there may be no need to resched right now, + if we keep on gathering more and more without flushing, + we'll be very unresponsive when a resched is needed later on. + + Consider the best suitable result between high performance and low latency + on preemption mode. + Select optimal munmap size to return memory space that is allocated by mmap system call. + + For example, For recording mass files, if we try to unmap memory that we allocated + with 100MB for recording in embedded devices, we have to wait for more than 3seconds to + change mode from play mode to recording mode. This results from the unit of memory + unmapped size when we are recording mass files like camcorder particularly. + + This value can be changed after boot using the + /proc/sys/vm/munmap_unit_size tunable. + + Examples: + 2048 => 8,388,608bytes : for straight-line efficiency + 1024 => 4,194,304bytes + 512 => 2,097,152bytes + 256 => 1,048,576bytes + 128 => 524,288bytes + 64 => 262,144bytes + 32 => 131,072bytes + 16 => 65,536bytes + 8 => 32,768bytes : for low-latency (*default) + +config PREEMPT_NO_MUNMAP_RANGE + int "Memory unmap unit on non-preemption mode (1024 => 4MB)" + depends on PREEMPT_NONE + range 8 2048 + default 1024 + help + + unmap_vmas(=unmap a range of memory covered by a list of vma) is treading + a delicate and uncomfortable line between hi-performance and low-latency. + We've chosen to improve performance at the expense of latency. + + So although there may be no need to resched right now, + if we keep on gathering more and more without flushing, + we'll be very unresponsive when a resched is needed later on. + + Consider the best suitable result between high performance and low latency + on preemption mode. + Select optimal munmap size to return memory space that is allocated by mmap system call. + + This value can be changed after boot using the + /proc/sys/vm/munmap_unit_size tunable. + + Examples: + 2048 => 8,388,608bytes : for straight-line efficiency + 1024 => 4,194,304bytes (*default) + 512 => 2,097,152bytes + 256 => 1,048,576bytes + 128 => 524,288bytes + 64 => 262,144bytes + 32 => 131,072bytes + 16 => 65,536bytes + 8 => 32,768bytes : for low-latency + # # Architectures with an unreliable sched_clock() should select this: # diff --git a/mm/memory.c b/mm/memory.c index ce22a25..e4533fe 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -57,6 +57,7 @@ #include <linux/swapops.h> #include <linux/elf.h> #include <linux/gfp.h> +#include <linux/munmap_unit_size.h> #include <asm/io.h> #include <asm/pgalloc.h> @@ -1079,6 +1080,10 @@ static unsigned long unmap_page_range(struct mmu_gather *tlb, (*zap_work)--; continue; } +#if 0 +printk("DEBUG:munmap step2,(%s:%d), unmap range = current(%lu) + \ +zap_work(%lu bytes) \n", current->comm, current->pid, addr, *zap_work); +#endif next = zap_pud_range(tlb, vma, pgd, addr, next, zap_work, details); } while (pgd++, addr = next, (addr != end && *zap_work > 0)); @@ -1088,12 +1093,10 @@ static unsigned long unmap_page_range(struct mmu_gather *tlb, return addr; } -#ifdef CONFIG_PREEMPT -# define ZAP_BLOCK_SIZE (8 * PAGE_SIZE) -#else -/* No preempt: go for improved straight-line efficiency */ -# define ZAP_BLOCK_SIZE (1024 * PAGE_SIZE) -#endif +/* No preempt: go for improved straight-line efficiency + * on PREEMPT(preemption mode) this is not a critical latency-path. + */ +# define ZAP_BLOCK_SIZE (munmap_unit_size * PAGE_SIZE) /** * unmap_vmas - unmap a range of memory covered by a list of vma's @@ -1133,7 +1136,11 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp, spinlock_t *i_mmap_lock = details? details->i_mmap_lock: NULL; int fullmm = (*tlbp)->fullmm; struct mm_struct *mm = vma->vm_mm; - +#if 0 +printk("DEBUG:munmap step1,(%s:%d), unit=zap_work(%ld)/ZAP_BLOCK(%ld), \ +vma:[%8lu]=%lu-%lu \n", current->comm, current->pid, zap_work, ZAP_BLOCK_SIZE, \ +vma->vm_end - vma->vm_start, vma->vm_end, vma->vm_start); +#endif mmu_notifier_invalidate_range_start(mm, start_addr, end_addr); for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next) { unsigned long end; -- 1.7.3.4 -- 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