Messages in this thread | | | Subject | Re: [RFC PATCH v3 6/7] scripts/sorttable: Add ORC unwind tables sort concurrently | From | Shile Zhang <> | Date | Fri, 15 Nov 2019 17:43:49 +0800 |
| |
On 2019/11/15 17:07, Peter Zijlstra wrote: > On Fri, Nov 15, 2019 at 02:47:49PM +0800, Shile Zhang wrote: > >> +#if defined(SORTTABLE_64) && defined(UNWINDER_ORC_ENABLED) >> +/* ORC unwinder only support X86_64 */ >> +#include <errno.h> >> +#include <pthread.h> >> +#include <linux/types.h> >> + >> +#define ORC_REG_UNDEFINED 0 >> +#define ERRSTRING_MAXSZ 256 >> + >> +struct orc_entry { >> + s16 sp_offset; >> + s16 bp_offset; >> + unsigned sp_reg:4; >> + unsigned bp_reg:4; >> + unsigned type:2; >> + unsigned end:1; >> +} __attribute__((packed)); >> + >> +struct orctable_info { >> + size_t orc_size; >> + size_t orc_ip_size; >> +} orctable; > There's ./arch/x86/include/asm/orc_types.h for this. Please don't > duplicate. objtool uses that same header. Good catch! Thanks for your kindly reminder! I'll remove it. >> +/** >> + * sort - sort an array of elements >> + * @base: pointer to data to sort >> + * @num: number of elements >> + * @size: size of each element >> + * @cmp_func: pointer to comparison function >> + * @swap_func: pointer to swap function >> + * >> + * This function does a heapsort on the given array. You may provide a >> + * swap_func function optimized to your element type. >> + * >> + * Sorting time is O(n log n) both on average and worst-case. While >> + * qsort is about 20% faster on average, it suffers from exploitable >> + * O(n*n) worst-case behavior and extra memory requirements that make >> + * it less suitable for kernel use. >> + * >> + * This code token out of /lib/sort.c. >> + */ >> +static void sort(void *base, size_t num, size_t size, >> + int (*cmp_func)(const void *, const void *), >> + void (*swap_func)(void *, void *, int size)) >> +{ >> + /* pre-scale counters for performance */ >> + int i = (num/2 - 1) * size, n = num * size, c, r; >> + >> + /* heapify */ >> + for ( ; i >= 0; i -= size) { >> + for (r = i; r * 2 + size < n; r = c) { >> + c = r * 2 + size; >> + if (c < n - size && >> + cmp_func(base + c, base + c + size) < 0) >> + c += size; >> + if (cmp_func(base + r, base + c) >= 0) >> + break; >> + swap_func(base + r, base + c, size); >> + } >> + } >> + >> + /* sort */ >> + for (i = n - size; i > 0; i -= size) { >> + swap_func(base, base + i, size); >> + for (r = 0; r * 2 + size < i; r = c) { >> + c = r * 2 + size; >> + if (c < i - size && >> + cmp_func(base + c, base + c + size) < 0) >> + c += size; >> + if (cmp_func(base + r, base + c) >= 0) >> + break; >> + swap_func(base + r, base + c, size); >> + } >> + } >> +} > Do we really need to copy the heapsort implementation? That is, why not > use libc's qsort() ? This is userspace after all.
Yes, I think qsort is better choice than copy-paste here. But qsort does not support customized swap func, which is needed for ORC unwind swap two tables together. I think it's hard to do with qsort, so I used sort same with original orc unwind table sort.
| |