diff options
Diffstat (limited to 'source/ap/squashfs-tools/0002-fix_phys_mem_calculation.patch')
| -rw-r--r-- | source/ap/squashfs-tools/0002-fix_phys_mem_calculation.patch | 159 |
1 files changed, 0 insertions, 159 deletions
diff --git a/source/ap/squashfs-tools/0002-fix_phys_mem_calculation.patch b/source/ap/squashfs-tools/0002-fix_phys_mem_calculation.patch deleted file mode 100644 index 20f9005b6..000000000 --- a/source/ap/squashfs-tools/0002-fix_phys_mem_calculation.patch +++ /dev/null @@ -1,159 +0,0 @@ -From 55f7ba830d40d438f0b0663a505e0c227fc68b6b Mon Sep 17 00:00:00 2001 -From: Phillip Lougher <phillip@squashfs.org.uk> -Date: Tue, 10 Jun 2014 21:51:52 +0100 -Subject: [PATCH] mksquashfs: fix phys mem calculation for 32-bit processes on - PAE/64-bit kernels - -When adding the code to base default memory usage on physical memory -(by default use 25% of physical memory), I made an oversight. I assumed -the process would be able to address 25% of physical memory. - -However, for 32-bit processes running on a PAE kernel or 64-bit kernel, -25% of physical memory can easily exceed the addressible memory for a -32-bit process, e.g. if a machine has 24 GB of physical memory, the -code would asume the process could easily use 6 GB. - -A 32-bit process by definition can only address 4 GB (32-bit pointers). -But, due to the typical kernel/user-space split (1GB/3GB, or 2GB/2GB) -on PAE kernels, a 32-bit process may only be able to address 2 GB. - -So, if Mksquashfs is a 32-bit application running on a PAE/64-bit kernel, -the code assumes it can address much more memory than it really can, which -means it runs out of memory. - -The fix is to impose a maximum default limit on 32-bit kernels, or -otherwise to never use a value more than 25% of the address space. If -we assume the maximum address space is 2 GB, then the maximum becomes -512 MB. But, given most kernels used the 1GB/3GB split, that may be -unduely conservative, and 25% of 3 GB (756 MB) may be better. This -patch compromises on 640 MB, which is mid-way between the 512 MB and 756 MB -values. It is also the fixed default value previously used by Mksquashfs. - -This patch also alters the code which imposes a maximum size. Previously -it was believed limiting to the physical memory size was adequate. But -obviously this needs to be updated to take into account a 32-bit process -may only be able to address 2 GB. In the process I've also taken the -opportunity to limit all requests to no more than 75% of physical memory. - -Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk> ---- - squashfs-tools/mksquashfs.c | 78 ++++++++++++++++++++++++++++++++++++++++----- - 1 file changed, 70 insertions(+), 8 deletions(-) - -diff --git a/squashfs-tools/mksquashfs.c b/squashfs-tools/mksquashfs.c -index 86f82bb..5370ecf 100644 ---- a/squashfs-tools/mksquashfs.c -+++ b/squashfs-tools/mksquashfs.c -@@ -304,7 +304,7 @@ void restorefs(); - struct dir_info *scan1_opendir(char *pathname, char *subpath, int depth); - void write_filesystem_tables(struct squashfs_super_block *sBlk, int nopad); - unsigned short get_checksum_mem(char *buff, int bytes); --int get_physical_memory(); -+void check_usable_phys_mem(int total_mem); - - - void prep_exit() -@@ -4053,11 +4053,7 @@ void initialise_threads(int readq, int fragq, int bwriteq, int fwriteq, - BAD_ERROR("Queue sizes rediculously too large\n"); - total_mem += fwriteq; - -- if(total_mem > get_physical_memory()) { -- ERROR("Total queue sizes larger than physical memory.\n"); -- ERROR("Mksquashfs will exhaust physical memory and thrash.\n"); -- BAD_ERROR("Queues too large\n"); -- } -+ check_usable_phys_mem(total_mem); - - /* - * convert from queue size in Mbytes to queue size in -@@ -4879,6 +4875,72 @@ int get_physical_memory() - } - - -+void check_usable_phys_mem(int total_mem) -+{ -+ /* -+ * We want to allow users to use as much of their physical -+ * memory as they wish. However, for practical reasons there are -+ * limits which need to be imposed, to protect users from themselves -+ * and to prevent people from using Mksquashfs as a DOS attack by using -+ * all physical memory. Mksquashfs uses memory to cache data from disk -+ * to optimise performance. It is pointless to ask it to use more -+ * than 75% of physical memory, as this causes thrashing and it is thus -+ * self-defeating. -+ */ -+ int mem = get_physical_memory(); -+ -+ mem = (mem >> 1) + (mem >> 2); /* 75% */ -+ -+ if(total_mem > mem) { -+ ERROR("Total memory requested is more than 75%% of physical " -+ "memory.\n"); -+ ERROR("Mksquashfs uses memory to cache data from disk to " -+ "optimise performance.\n"); -+ ERROR("It is pointless to ask it to use more than this amount " -+ "of memory, as this\n"); -+ ERROR("causes thrashing and it is thus self-defeating.\n"); -+ BAD_ERROR("Requested memory size too large\n"); -+ } -+ -+ if(sizeof(void *) == 4 && total_mem > 2048) { -+ /* -+ * If we're running on a kernel with PAE or on a 64-bit kernel, -+ * then the 75% physical memory limit can still easily exceed -+ * the addressable memory by this process. -+ * -+ * Due to the typical kernel/user-space split (1GB/3GB, or -+ * 2GB/2GB), we have to conservatively assume the 32-bit -+ * processes can only address 2-3GB. So refuse if the user -+ * tries to allocate more than 2GB. -+ */ -+ ERROR("Total memory requested may exceed maximum " -+ "addressable memory by this process\n"); -+ BAD_ERROR("Requested memory size too large\n"); -+ } -+} -+ -+ -+int get_default_phys_mem() -+{ -+ int mem = get_physical_memory() / SQUASHFS_TAKE; -+ -+ if(sizeof(void *) == 4 && mem > 640) { -+ /* -+ * If we're running on a kernel with PAE or on a 64-bit kernel, -+ * the default memory usage can exceed the addressable -+ * memory by this process. -+ * Due to the typical kernel/user-space split (1GB/3GB, or -+ * 2GB/2GB), we have to conservatively assume the 32-bit -+ * processes can only address 2-3GB. So limit the default -+ * usage to 640M, which gives room for other data. -+ */ -+ mem = 640; -+ } -+ -+ return mem; -+} -+ -+ - void calculate_queue_sizes(int mem, int *readq, int *fragq, int *bwriteq, - int *fwriteq) - { -@@ -4890,7 +4952,7 @@ void calculate_queue_sizes(int mem, int *readq, int *fragq, int *bwriteq, - - - #define VERSION() \ -- printf("mksquashfs version 4.3 (2014/05/12)\n");\ -+ printf("mksquashfs version 4.3-git (2014/06/09)\n");\ - printf("copyright (C) 2014 Phillip Lougher "\ - "<phillip@squashfs.org.uk>\n\n"); \ - printf("This program is free software; you can redistribute it and/or"\ -@@ -4918,7 +4980,7 @@ int main(int argc, char *argv[]) - int fragq; - int bwriteq; - int fwriteq; -- int total_mem = get_physical_memory() / SQUASHFS_TAKE; -+ int total_mem = get_default_phys_mem(); - int progress = TRUE; - int force_progress = FALSE; - struct file_buffer **fragment = NULL; |