Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751908AbaABHO0 (ORCPT ); Thu, 2 Jan 2014 02:14:26 -0500 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:61829 "EHLO LGEMRELSE7Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751039AbaABHNL (ORCPT ); Thu, 2 Jan 2014 02:13:11 -0500 X-AuditID: 9c930197-b7c4aae000003d84-07-52c511849f4f From: Minchan Kim To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , Mel Gorman , Hugh Dickins , Dave Hansen , Rik van Riel , KOSAKI Motohiro , Michel Lespinasse , Johannes Weiner , John Stultz , Dhaval Giani , "H. Peter Anvin" , Android Kernel Team , Robert Love , Mel Gorman , Dmitry Adamushko , Dave Chinner , Neil Brown , Andrea Righi , Andrea Arcangeli , "Aneesh Kumar K.V" , Mike Hommey , Taras Glek , Jan Kara , KOSAKI Motohiro , Rob Clark , Jason Evans , Minchan Kim Subject: [PATCH v10 04/16] vrange: Add new vrange(2) system call Date: Thu, 2 Jan 2014 16:12:12 +0900 Message-Id: <1388646744-15608-5-git-send-email-minchan@kernel.org> X-Mailer: git-send-email 1.8.5.2 In-Reply-To: <1388646744-15608-1-git-send-email-minchan@kernel.org> References: <1388646744-15608-1-git-send-email-minchan@kernel.org> X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10183 Lines: 332 This patch adds new system call sys_vrange. NAME vrange - Mark or unmark range of memory as volatile SYNOPSIS int vrange(unsigned_long start, size_t length, int mode, int *purged); DESCRIPTION Applications can use vrange(2) to advise the kernel how it should handle paging I/O in this VM area. The idea is to help the kernel discard pages of vrange instead of reclaiming when memory pressure happens. It means kernel doesn't discard any pages of vrange if there is no memory pressure. mode: VRANGE_VOLATILE hint to kernel so VM can discard in vrange pages when memory pressure happens. VRANGE_NONVOLATILE hint to kernel so VM doesn't discard vrange pages any more. If user try to access purged memory without VRANGE_NOVOLATILE call, he can encounter SIGBUS if the page was discarded by kernel. purged: Pointer to an integer which will return 1 if mode == VRANGE_NONVOLATILE and any page in the affected range was purged. If purged returns zero during a mode == VRANGE_NONVOLATILE call, it means all of the pages in the range are intact. RETURN VALUE On success vrange returns the number of bytes marked or unmarked. Similar to write(), it may return fewer bytes then specified if it ran into a problem. If an error is returned, no changes were made. ERRORS EINVAL This error can occur for the following reasons: * The value length is negative or not page size units. * addr is not page-aligned * mode not a valid value. ENOMEM Not enough memory EFAULT purged pointer is invalid There were some comment about this interface. Firstly, it was suggested by part of madvise(2) but there were some reason to make it hard. o Why is it hard to make it based on madvise(2) and vm_area_struct? The madvise syscall logic is based on vma split/merging but vrange syscall want to avoid it because it requires mmap_sem which is very coarse-graind lock and it is critical for multi-threaded friendly userspace allocator and vma split/merge could create lots of vm_area_struct because we don't want to merge adjacent volatile ranges so that we would support fine-grained purging without propagating purging into another volatile ranges. For exmaple, firefox folks want to make volatile range as page unit so if we create vm_area_struct per PAGE_SIZE range, memory footprint will be much bigger. Cc: Android Kernel Team Cc: Robert Love Cc: Mel Gorman Cc: Hugh Dickins Cc: Dave Hansen Cc: Rik van Riel Cc: Dmitry Adamushko Cc: Dave Chinner Cc: Neil Brown Cc: Andrea Righi Cc: Andrea Arcangeli Cc: Aneesh Kumar K.V Cc: Mike Hommey Cc: Taras Glek Cc: Dhaval Giani Cc: Jan Kara Cc: KOSAKI Motohiro Cc: Michel Lespinasse Cc: Johannes Weiner Cc: Rob Clark Cc: linux-mm@kvack.org Signed-off-by: Minchan Kim Signed-off-by: John Stultz --- arch/x86/syscalls/syscall_64.tbl | 1 + include/linux/syscalls.h | 2 + include/uapi/asm-generic/mman-common.h | 3 + kernel/sys_ni.c | 1 + mm/vrange.c | 164 ++++++++++++++++++++++++++++++++ 5 files changed, 171 insertions(+) diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl index 38ae65dfd14f..dc332bdc3514 100644 --- a/arch/x86/syscalls/syscall_64.tbl +++ b/arch/x86/syscalls/syscall_64.tbl @@ -320,6 +320,7 @@ 311 64 process_vm_writev sys_process_vm_writev 312 common kcmp sys_kcmp 313 common finit_module sys_finit_module +314 common vrange sys_vrange # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 7fac04e7ff6e..2c56f954effe 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -847,4 +847,6 @@ asmlinkage long sys_process_vm_writev(pid_t pid, asmlinkage long sys_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, unsigned long idx2); asmlinkage long sys_finit_module(int fd, const char __user *uargs, int flags); +asmlinkage long sys_vrange(unsigned long start, size_t len, int mode, + int __user *purged); #endif diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h index 4164529a94f9..9be120b3b33f 100644 --- a/include/uapi/asm-generic/mman-common.h +++ b/include/uapi/asm-generic/mman-common.h @@ -66,4 +66,7 @@ #define MAP_HUGE_SHIFT 26 #define MAP_HUGE_MASK 0x3f +#define VRANGE_VOLATILE 0 /* unpin pages so VM can discard them */ +#define VRANGE_NONVOLATILE 1 /* pin pages so VM can't discard them */ + #endif /* __ASM_GENERIC_MMAN_COMMON_H */ diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index 7078052284fd..f40070eff8a1 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -175,6 +175,7 @@ cond_syscall(sys_mremap); cond_syscall(sys_remap_file_pages); cond_syscall(compat_sys_move_pages); cond_syscall(compat_sys_migrate_pages); +cond_syscall(sys_vrange); /* block-layer dependent */ cond_syscall(sys_bdflush); diff --git a/mm/vrange.c b/mm/vrange.c index 444da8794dbf..9ed5610b2e54 100644 --- a/mm/vrange.c +++ b/mm/vrange.c @@ -4,6 +4,8 @@ #include #include +#include +#include static struct kmem_cache *vrange_cachep; @@ -230,3 +232,165 @@ fail: vrange_root_cleanup(new); return -ENOMEM; } + +static inline struct vrange_root *__vma_to_vroot(struct vm_area_struct *vma) +{ + struct vrange_root *vroot = NULL; + + if (vma->vm_file && (vma->vm_flags & VM_SHARED)) + vroot = &vma->vm_file->f_mapping->vroot; + else + vroot = &vma->vm_mm->vroot; + return vroot; +} + +static inline unsigned long __vma_addr_to_index(struct vm_area_struct *vma, + unsigned long addr) +{ + if (vma->vm_file && (vma->vm_flags & VM_SHARED)) + return (vma->vm_pgoff << PAGE_SHIFT) + addr - vma->vm_start; + return addr; +} + +static ssize_t do_vrange(struct mm_struct *mm, unsigned long start_idx, + unsigned long end_idx, int mode, int *purged) +{ + struct vm_area_struct *vma; + unsigned long orig_start = start_idx; + ssize_t count = 0, ret = 0; + + down_read(&mm->mmap_sem); + + vma = find_vma(mm, start_idx); + for (;;) { + struct vrange_root *vroot; + unsigned long tmp, vstart_idx, vend_idx; + + if (!vma) + goto out; + + if (vma->vm_flags & (VM_SPECIAL|VM_LOCKED|VM_MIXEDMAP| + VM_HUGETLB)) + goto out; + + /* make sure start is at the front of the current vma*/ + if (start_idx < vma->vm_start) { + start_idx = vma->vm_start; + if (start_idx > end_idx) + goto out; + } + + /* bound tmp to closer of vm_end & end */ + tmp = vma->vm_end - 1; + if (end_idx < tmp) + tmp = end_idx; + + vroot = __vma_to_vroot(vma); + vstart_idx = __vma_addr_to_index(vma, start_idx); + vend_idx = __vma_addr_to_index(vma, tmp); + + /* mark or unmark */ + if (mode == VRANGE_VOLATILE) + ret = vrange_add(vroot, vstart_idx, vend_idx); + else if (mode == VRANGE_NONVOLATILE) + ret = vrange_remove(vroot, vstart_idx, vend_idx, + purged); + + if (ret) + goto out; + + /* update count to distance covered so far*/ + count = tmp - orig_start + 1; + + /* move start up to the end of the vma*/ + start_idx = vma->vm_end; + if (start_idx > end_idx) + goto out; + /* move to the next vma */ + vma = vma->vm_next; + } +out: + up_read(&mm->mmap_sem); + + /* report bytes successfully marked, even if we're exiting on error */ + if (count) + return count; + + return ret; +} + +/* + * The vrange(2) system call. + * + * Applications can use vrange() to advise the kernel how it should + * handle paging I/O in this VM area. The idea is to help the kernel + * discard pages of vrange instead of swapping out when memory pressure + * happens. The information provided is advisory only, and can be safely + * disregarded by the kernel if system has enough free memory. + * + * mode values: + * VRANGE_VOLATILE - hint to kernel so VM can discard vrange pages when + * memory pressure happens. + * VRANGE_NONVOLATILE - Removes any volatile hints previous specified in that + * range. + * + * purged ptr: + * Returns 1 if any page in the range being marked nonvolatile has been purged. + * + * Return values: + * On success vrange returns the number of bytes marked or unmarked. + * Similar to write(), it may return fewer bytes then specified if + * it ran into a problem. + * + * If an error is returned, no changes were made. + * + * Errors: + * -EINVAL - start len < 0, start is not page-aligned, start is greater + * than TASK_SIZE or "mode" is not a valid value. + * -ENOMEM - Short of free memory in system for successful system call. + * -EFAULT - Purged pointer is invalid. + * -ENOSUP - Feature not yet supported. + */ +SYSCALL_DEFINE4(vrange, unsigned long, start, + size_t, len, int, mode, int __user *, purged) +{ + unsigned long end; + struct mm_struct *mm = current->mm; + ssize_t ret = -EINVAL; + int p = 0; + + if (start & ~PAGE_MASK) + goto out; + + len &= PAGE_MASK; + if (!len) + goto out; + + end = start + len; + if (end < start) + goto out; + + if (start >= TASK_SIZE) + goto out; + + if (purged) { + /* Test pointer is valid before making any changes */ + if (put_user(p, purged)) + return -EFAULT; + } + + ret = do_vrange(mm, start, end - 1, mode, &p); + + if (purged) { + if (put_user(p, purged)) { + /* + * This would be bad, since we've modified volatilty + * and the change in purged state would be lost. + */ + BUG(); + } + } + +out: + return ret; +} -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/