The branch stable/13 has been updated by dougm: URL: https://cgit.FreeBSD.org/src/commit/?id=35b262e57114adfa8064c66b9ab83fc60e11fa81
commit 35b262e57114adfa8064c66b9ab83fc60e11fa81 Author: Doug Moore <[email protected]> AuthorDate: 2022-08-29 16:11:31 +0000 Commit: Doug Moore <[email protected]> CommitDate: 2022-09-19 02:39:21 +0000 rb_tree: avoid extra reads in rebalancing In RB_INSERT_COLOR and RB_REMOVE_COLOR, avoid reading a parent pointer from memory, and then reading the left-color bit from memory, and then reading the right-color bit from memory, since they're all in the same field. The compiler can't infer that only the first read is really necessary, so write the code in a way so that it doesn't have to. Drop RB_RED_LEFT and RB_RED_RIGHT macros that reach into memory to get those bits. Drop RB_COLOR, the only thing left using RB_RED_LEFT and RB_RED_RIGHT after the other changes, and go straight to DIAGNOSTIC code in subr_stats to implement RB_COLOR for its single, dubious use there. Reviewed by: alc MFC after: 3 weeks Differential Revision: https://reviews.freebsd.org/D36353 (cherry picked from commit 5d91386826d0f360d87ce3f39c9ebf266f149325) --- sys/kern/subr_stats.c | 9 +++++- sys/sys/tree.h | 82 +++++++++++++++++++++++++++------------------------ 2 files changed, 52 insertions(+), 39 deletions(-) diff --git a/sys/kern/subr_stats.c b/sys/kern/subr_stats.c index 946999263898..0984d2a21014 100644 --- a/sys/kern/subr_stats.c +++ b/sys/kern/subr_stats.c @@ -3406,6 +3406,13 @@ stats_v1_vsd_tdgst_add(enum vsd_dtype vs_dtype, struct voistatdata_tdgst *tdgst, Q_TOSTR(rbctd64->mu, -1, 10, qstr, sizeof(qstr)); + struct voistatdata_tdgstctd64 *parent; + parent = RB_PARENT(rbctd64, rblnk); + int rb_color = + parent == NULL ? 0 : + RB_LEFT(parent, rblnk) == rbctd64 ? + (RB_BITS(parent, rblnk) & RB_RED_L) != 0 : + (RB_BITS(parent, rblnk) & RB_RED_R) != 0; printf(" RB ctd=%3d p=%3d l=%3d r=%3d c=%2d " "mu=%s\n", (int)ARB_SELFIDX(ctd64tree, rbctd64), @@ -3415,7 +3422,7 @@ stats_v1_vsd_tdgst_add(enum vsd_dtype vs_dtype, struct voistatdata_tdgst *tdgst, RB_LEFT(rbctd64, rblnk)), (int)ARB_SELFIDX(ctd64tree, RB_RIGHT(rbctd64, rblnk)), - RB_COLOR(rbctd64, rblnk), + rb_color, qstr); panic("RB@%p and ARB@%p trees differ\n", diff --git a/sys/sys/tree.h b/sys/sys/tree.h index 38c82c4e4a52..3f1735d2a837 100644 --- a/sys/sys/tree.h +++ b/sys/sys/tree.h @@ -341,8 +341,6 @@ struct { \ #define RB_FLIP_LEFT(elm, field) (RB_BITS(elm, field) ^= RB_RED_L) #define RB_FLIP_RIGHT(elm, field) (RB_BITS(elm, field) ^= RB_RED_R) #define RB_FLIP_ALL(elm, field) (RB_BITS(elm, field) ^= RB_RED_MASK) -#define RB_RED_LEFT(elm, field) ((RB_BITS(elm, field) & RB_RED_L) != 0) -#define RB_RED_RIGHT(elm, field) ((RB_BITS(elm, field) & RB_RED_R) != 0) #define _RB_PARENT_ONLY(elm) (__typeof(elm)) \ ((__uintptr_t)elm & ~RB_RED_MASK) #define RB_PARENT(elm, field) _RB_PARENT_ONLY(RB_UP(elm, field)) @@ -359,11 +357,6 @@ struct { \ RB_LEFT(elm, field) = RB_RIGHT(elm, field) = NULL; \ } while (/*CONSTCOND*/ 0) -#define RB_COLOR(elm, field) (RB_PARENT(elm, field) == NULL ? 0 : \ - RB_LEFT(RB_PARENT(elm, field), field) == elm ? \ - RB_RED_LEFT(RB_PARENT(elm, field), field) : \ - RB_RED_RIGHT(RB_PARENT(elm, field), field)) - /* * Something to be invoked in a loop at the root of every modified subtree, * from the bottom up to the root, to update augmented node data. @@ -489,67 +482,72 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm) \ * when a value has been assigned to 'child' in the previous \ * one. \ */ \ - struct type *child, *gpar, *parent; \ - while ((parent = RB_PARENT(elm, field)) != NULL) { \ - gpar = RB_PARENT(parent, field); \ + struct type *child, *gpar = RB_UP(elm, field), *parent; \ + __uintptr_t red; \ + \ + while ((parent = gpar) != NULL) { \ + red = RB_BITS(parent, field); \ + gpar = RB_UP(parent, field); \ if (RB_LEFT(parent, field) == elm) { \ - if (RB_RED_LEFT(parent, field)) { \ + if (red & RB_RED_L) { \ RB_FLIP_LEFT(parent, field); \ return; \ } \ RB_FLIP_RIGHT(parent, field); \ - if (RB_RED_RIGHT(parent, field)) { \ + if ((red & RB_RED_MASK) == 0) { \ child = elm; \ elm = parent; \ continue; \ } \ - if (RB_RED_RIGHT(elm, field)) \ + red = RB_BITS(elm, field); \ + if (red & RB_RED_R) \ child = elm; \ else { \ /* coverity[uninit_use] */ \ RB_ROTATE_LEFT(elm, child, field); \ - if (RB_RED_RIGHT(child, field)) \ + red = RB_BITS(child, field); \ + if (red & RB_RED_R) \ RB_FLIP_LEFT(parent, field); \ - if (RB_RED_LEFT(child, field)) \ + if (red & RB_RED_L) \ RB_FLIP_ALL(elm, field); \ else \ RB_FLIP_LEFT(elm, field); \ - if ((RB_BITS(child, field) & \ - RB_RED_MASK) == 0) \ + if ((red & RB_RED_MASK) == 0) \ elm = child; \ } \ RB_ROTATE_RIGHT(parent, child, field); \ } else { \ - if (RB_RED_RIGHT(parent, field)) { \ + if (red & RB_RED_R) { \ RB_FLIP_RIGHT(parent, field); \ return; \ } \ RB_FLIP_LEFT(parent, field); \ - if (RB_RED_LEFT(parent, field)) { \ + if ((red & RB_RED_MASK) == 0) { \ child = elm; \ elm = parent; \ continue; \ } \ - if (RB_RED_LEFT(elm, field)) \ + red = RB_BITS(elm, field); \ + if (red & RB_RED_L) \ child = elm; \ else { \ /* coverity[uninit_use] */ \ RB_ROTATE_RIGHT(elm, child, field); \ - if (RB_RED_LEFT(child, field)) \ + red = RB_BITS(child, field); \ + if (red & RB_RED_L) \ RB_FLIP_RIGHT(parent, field); \ - if (RB_RED_RIGHT(child, field)) \ + if (red & RB_RED_R) \ RB_FLIP_ALL(elm, field); \ else \ RB_FLIP_RIGHT(elm, field); \ - if ((RB_BITS(child, field) & \ - RB_RED_MASK) == 0) \ + if ((red & RB_RED_MASK) == 0) \ elm = child; \ } \ RB_ROTATE_LEFT(parent, child, field); \ } \ - RB_SET_PARENT(child, gpar, field); \ + gpar = _RB_PARENT_ONLY(gpar); \ + RB_UP(child, field) = gpar; \ RB_SWAP_CHILD(head, gpar, parent, child, field); \ - RB_BITS(child, field) &= ~RB_RED_MASK; \ if (elm != child) \ RB_AUGMENT(elm); \ RB_AUGMENT(parent); \ @@ -574,6 +572,8 @@ name##_RB_REMOVE_COLOR(struct name *head, \ struct type *parent, struct type *elm) \ { \ struct type *gpar, *sib; \ + __uintptr_t red; \ + \ if (RB_LEFT(parent, field) == elm && \ RB_RIGHT(parent, field) == elm) { \ RB_BITS(parent, field) &= ~RB_RED_MASK; \ @@ -583,19 +583,21 @@ name##_RB_REMOVE_COLOR(struct name *head, \ return; \ } \ do { \ - gpar = RB_PARENT(parent, field); \ + red = RB_BITS(parent, field); \ + gpar = RB_UP(parent, field); \ if (RB_LEFT(parent, field) == elm) { \ - if (!RB_RED_LEFT(parent, field)) { \ + if (~red & RB_RED_L) { \ RB_FLIP_LEFT(parent, field); \ return; \ } \ - if (RB_RED_RIGHT(parent, field)) { \ + if ((~red & RB_RED_MASK) == 0) { \ RB_FLIP_RIGHT(parent, field); \ elm = parent; \ continue; \ } \ sib = RB_RIGHT(parent, field); \ - switch (RB_BITS(sib, field) & RB_RED_MASK) { \ + red = RB_BITS(sib, field); \ + switch (red & RB_RED_MASK) { \ case RB_RED_MASK: \ RB_FLIP_ALL(sib, field); \ elm = parent; \ @@ -603,11 +605,12 @@ name##_RB_REMOVE_COLOR(struct name *head, \ case RB_RED_R: \ elm = RB_LEFT(sib, field); \ RB_ROTATE_RIGHT(sib, elm, field); \ - if (RB_RED_LEFT(elm, field)) \ + red = RB_BITS(elm, field); \ + if (red & RB_RED_L) \ RB_FLIP_ALL(parent, field); \ else \ RB_FLIP_LEFT(parent, field); \ - if (RB_RED_RIGHT(elm, field)) \ + if (red & RB_RED_R) \ RB_FLIP_ALL(sib, field); \ else \ RB_FLIP_RIGHT(sib, field); \ @@ -629,17 +632,18 @@ name##_RB_REMOVE_COLOR(struct name *head, \ } \ RB_ROTATE_LEFT(parent, elm, field); \ } else { \ - if (!RB_RED_RIGHT(parent, field)) { \ + if (~red & RB_RED_R) { \ RB_FLIP_RIGHT(parent, field); \ return; \ } \ - if (RB_RED_LEFT(parent, field)) { \ + if ((~red & RB_RED_MASK) == 0) { \ RB_FLIP_LEFT(parent, field); \ elm = parent; \ continue; \ } \ sib = RB_LEFT(parent, field); \ - switch (RB_BITS(sib, field) & RB_RED_MASK) { \ + red = RB_BITS(sib, field); \ + switch (red & RB_RED_MASK) { \ case RB_RED_MASK: \ RB_FLIP_ALL(sib, field); \ elm = parent; \ @@ -647,11 +651,12 @@ name##_RB_REMOVE_COLOR(struct name *head, \ case RB_RED_L: \ elm = RB_RIGHT(sib, field); \ RB_ROTATE_LEFT(sib, elm, field); \ - if (RB_RED_RIGHT(elm, field)) \ + red = RB_BITS(elm, field); \ + if (red & RB_RED_R) \ RB_FLIP_ALL(parent, field); \ else \ RB_FLIP_RIGHT(parent, field); \ - if (RB_RED_LEFT(elm, field)) \ + if (red & RB_RED_L) \ RB_FLIP_ALL(sib, field); \ else \ RB_FLIP_LEFT(sib, field); \ @@ -673,12 +678,13 @@ name##_RB_REMOVE_COLOR(struct name *head, \ } \ RB_ROTATE_RIGHT(parent, elm, field); \ } \ + gpar = _RB_PARENT_ONLY(gpar); \ RB_SET_PARENT(elm, gpar, field); \ RB_SWAP_CHILD(head, gpar, parent, elm, field); \ if (sib != elm) \ RB_AUGMENT(sib); \ break; \ - } while ((parent = RB_PARENT(elm, field)) != NULL); \ + } while ((parent = _RB_PARENT_ONLY(gpar)) != NULL); \ } #define RB_GENERATE_REMOVE(name, type, field, attr) \
