From patchwork Fri Jun 2 23:39:23 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Emilio Cota X-Patchwork-Id: 9763685 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 40B9260360 for ; Fri, 2 Jun 2017 23:40:16 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 29728285DC for ; Fri, 2 Jun 2017 23:40:16 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1DF66285E2; Fri, 2 Jun 2017 23:40:16 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 2025C285DC for ; Fri, 2 Jun 2017 23:40:14 +0000 (UTC) Received: from localhost ([::1]:51831 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dGwAs-0001Ss-V5 for patchwork-qemu-devel@patchwork.kernel.org; Fri, 02 Jun 2017 19:40:10 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48997) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dGwAE-0001Sm-QN for qemu-devel@nongnu.org; Fri, 02 Jun 2017 19:39:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dGwAA-000722-Qg for qemu-devel@nongnu.org; Fri, 02 Jun 2017 19:39:30 -0400 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:36801) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dGwAA-0006xc-Dr for qemu-devel@nongnu.org; Fri, 02 Jun 2017 19:39:26 -0400 Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailout.nyi.internal (Postfix) with ESMTP id 1FF862089B; Fri, 2 Jun 2017 19:39:24 -0400 (EDT) Received: from frontend2 ([10.202.2.161]) by compute4.internal (MEProxy); Fri, 02 Jun 2017 19:39:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=braap.org; h=cc :date:from:in-reply-to:message-id:references:subject:to :x-me-sender:x-me-sender:x-sasl-enc:x-sasl-enc; s=mesmtp; bh=raj 2YQaykTwAOgKWXllg1EYeqznUaeNNGeNDVAPGfX8=; b=asNh4sjO/4hRg3WmatN zfsnfq7bLspsyMblKfvsZmyCxVcBXv2sqwdFAmavZtxXI9z55Y6jVPkx69otesHp 0KfudCi0Oypev1NYX2dgQaw2pw7CKvuKlZxbc6sVx/emPrjvng3gXwjUSMNxupnF VQZmPu8DlmPf8CXMcAU2wcvM= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:date:from:in-reply-to:message-id :references:subject:to:x-me-sender:x-me-sender:x-sasl-enc :x-sasl-enc; s=fm1; bh=raj2YQaykTwAOgKWXllg1EYeqznUaeNNGeNDVAPGf X8=; b=J+/Zmm2bqz/W3hd0ceWZ+/PacZtbm31Vro0rsuI2YbjlD35fJsmv836pZ JT1sO+onSBsOiGxFJdeIOM5tQBch8PhS9zDHKVmBOJQrkwQPEHNjjpSE0YhFpRNX 3hidgkPZv3J0AxCicjCfEZJ2SOGhLN2hEhyz47gD/RhEVEv0RSOe63B8H4iDjqRj anKCBEj3MhXVQfuK/LrfSeGOLc+rphl0XaV6Yd8SkGNNvLbdyLsqzXzSF+btWqDV fQOsmXcTrRk+8wV5qNpaU6+xfRmzSAznsILkccUYCOXjztitovWnsUMARNAk0Prr 58A8FNFXBCnjxubW4vjKXnkDWtqCw== X-ME-Sender: X-Sasl-enc: t0sGf68Tz4yaswYZMutG072RedGsa8dBW1tllt5kDwD2 1496446763 Received: from localhost (flamenco.cs.columbia.edu [128.59.20.216]) by mail.messagingengine.com (Postfix) with ESMTPA id CF1C324814; Fri, 2 Jun 2017 19:39:23 -0400 (EDT) From: "Emilio G. Cota" To: qemu-devel@nongnu.org Date: Fri, 2 Jun 2017 19:39:23 -0400 Message-Id: <1496446763-29756-1-git-send-email-cota@braap.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1e67644b-4b30-887e-d329-1848e94c9484@twiddle.net> References: <1e67644b-4b30-887e-d329-1848e94c9484@twiddle.net> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.111.4.25 Subject: [Qemu-devel] [PATCH] tcg: allocate TB structs before the corresponding translated code X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Pranith Kumar , Paolo Bonzini , alex.bennee@linaro.org, Richard Henderson Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP Allocating an arbitrarily-sized array of tbs results in either (a) a lot of memory wasted or (b) unnecessary flushes of the code cache when we run out of TB structs in the array. An obvious solution would be to just malloc a TB struct when needed, and keep the TB array as an array of pointers (recall that tb_find_pc() needs the TB array to run in O(log n)). Perhaps a better solution, which is implemented in this patch, is to allocate TB's right before the translated code they describe. This results in some memory waste due to padding to have code and TBs in separate cache lines--for instance, I measured 4.7% of padding in the used portion of code_gen_buffer when booting Linux on aarch64. However, it can allow for optimizations in some host architectures, since TCG backends could safely assume that the TB and the corresponding translated code are very close to each other in memory. See this message by rth for a detailed explanation: https://lists.gnu.org/archive/html/qemu-devel/2017-03/msg05172.html Subject: Re: GSoC 2017 Proposal: TCG performance enhancements Message-ID: <1e67644b-4b30-887e-d329-1848e94c9484@twiddle.net> Note: this patch applies on top of rth's tcg-next branch (a34a15462). Suggested-by: Richard Henderson Signed-off-by: Emilio G. Cota --- include/exec/exec-all.h | 2 +- include/exec/tb-context.h | 3 ++- tcg/tcg.c | 16 ++++++++++++++++ tcg/tcg.h | 2 +- translate-all.c | 37 ++++++++++++++++++++++--------------- 5 files changed, 42 insertions(+), 18 deletions(-) diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index 87ae10b..e431548 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -363,7 +363,7 @@ struct TranslationBlock { */ uintptr_t jmp_list_next[2]; uintptr_t jmp_list_first; -}; +} QEMU_ALIGNED(64); void tb_free(TranslationBlock *tb); void tb_flush(CPUState *cpu); diff --git a/include/exec/tb-context.h b/include/exec/tb-context.h index c7f17f2..25c2afe 100644 --- a/include/exec/tb-context.h +++ b/include/exec/tb-context.h @@ -31,8 +31,9 @@ typedef struct TBContext TBContext; struct TBContext { - TranslationBlock *tbs; + TranslationBlock **tbs; struct qht htable; + size_t tbs_size; int nb_tbs; /* any access to the tbs or the page table must use this lock */ QemuMutex tb_lock; diff --git a/tcg/tcg.c b/tcg/tcg.c index cb898f1..1e9da5b 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -383,6 +383,22 @@ void tcg_context_init(TCGContext *s) } } +/* + * Allocate TBs right before their corresponding translated code, making + * sure that TBs and code are on different cache lines. + */ +TranslationBlock *tcg_tb_alloc(TCGContext *s) +{ + void *aligned; + + aligned = (void *)ROUND_UP((uintptr_t)s->code_gen_ptr, 64); + if (unlikely(aligned + sizeof(TranslationBlock) > s->code_gen_highwater)) { + return NULL; + } + s->code_gen_ptr += aligned - s->code_gen_ptr + sizeof(TranslationBlock); + return aligned; +} + void tcg_prologue_init(TCGContext *s) { size_t prologue_size, total_size; diff --git a/tcg/tcg.h b/tcg/tcg.h index 5ec48d1..9e37722 100644 --- a/tcg/tcg.h +++ b/tcg/tcg.h @@ -697,7 +697,6 @@ struct TCGContext { here, because there's too much arithmetic throughout that relies on addition and subtraction working on bytes. Rely on the GCC extension that allows arithmetic on void*. */ - int code_gen_max_blocks; void *code_gen_prologue; void *code_gen_epilogue; void *code_gen_buffer; @@ -756,6 +755,7 @@ static inline bool tcg_op_buf_full(void) /* tb_lock must be held for tcg_malloc_internal. */ void *tcg_malloc_internal(TCGContext *s, int size); void tcg_pool_reset(TCGContext *s); +TranslationBlock *tcg_tb_alloc(TCGContext *s); void tb_lock(void); void tb_unlock(void); diff --git a/translate-all.c b/translate-all.c index b3ee876..e36c4d0 100644 --- a/translate-all.c +++ b/translate-all.c @@ -781,12 +781,13 @@ static inline void code_gen_alloc(size_t tb_size) exit(1); } - /* Estimate a good size for the number of TBs we can support. We - still haven't deducted the prologue from the buffer size here, - but that's minimal and won't affect the estimate much. */ - tcg_ctx.code_gen_max_blocks - = tcg_ctx.code_gen_buffer_size / CODE_GEN_AVG_BLOCK_SIZE; - tcg_ctx.tb_ctx.tbs = g_new(TranslationBlock, tcg_ctx.code_gen_max_blocks); + /* size this conservatively -- realloc later if needed */ + tcg_ctx.tb_ctx.tbs_size = + tcg_ctx.code_gen_buffer_size / CODE_GEN_AVG_BLOCK_SIZE / 8; + if (unlikely(!tcg_ctx.tb_ctx.tbs_size)) { + tcg_ctx.tb_ctx.tbs_size = 1024; + } + tcg_ctx.tb_ctx.tbs = g_new(TranslationBlock *, tcg_ctx.tb_ctx.tbs_size); qemu_mutex_init(&tcg_ctx.tb_ctx.tb_lock); } @@ -828,13 +829,20 @@ bool tcg_enabled(void) static TranslationBlock *tb_alloc(target_ulong pc) { TranslationBlock *tb; + TBContext *ctx; assert_tb_locked(); - if (tcg_ctx.tb_ctx.nb_tbs >= tcg_ctx.code_gen_max_blocks) { + tb = tcg_tb_alloc(&tcg_ctx); + if (unlikely(tb == NULL)) { return NULL; } - tb = &tcg_ctx.tb_ctx.tbs[tcg_ctx.tb_ctx.nb_tbs++]; + ctx = &tcg_ctx.tb_ctx; + if (unlikely(ctx->nb_tbs == ctx->tbs_size)) { + ctx->tbs_size *= 2; + ctx->tbs = g_renew(TranslationBlock *, ctx->tbs, ctx->tbs_size); + } + ctx->tbs[ctx->nb_tbs++] = tb; tb->pc = pc; tb->cflags = 0; tb->invalid = false; @@ -850,8 +858,8 @@ void tb_free(TranslationBlock *tb) Ignore the hard cases and just back up if this TB happens to be the last one generated. */ if (tcg_ctx.tb_ctx.nb_tbs > 0 && - tb == &tcg_ctx.tb_ctx.tbs[tcg_ctx.tb_ctx.nb_tbs - 1]) { - tcg_ctx.code_gen_ptr = tb->tc_ptr; + tb == tcg_ctx.tb_ctx.tbs[tcg_ctx.tb_ctx.nb_tbs - 1]) { + tcg_ctx.code_gen_ptr = tb->tc_ptr - sizeof(TranslationBlock); tcg_ctx.tb_ctx.nb_tbs--; } } @@ -1666,7 +1674,7 @@ static TranslationBlock *tb_find_pc(uintptr_t tc_ptr) m_max = tcg_ctx.tb_ctx.nb_tbs - 1; while (m_min <= m_max) { m = (m_min + m_max) >> 1; - tb = &tcg_ctx.tb_ctx.tbs[m]; + tb = tcg_ctx.tb_ctx.tbs[m]; v = (uintptr_t)tb->tc_ptr; if (v == tc_ptr) { return tb; @@ -1676,7 +1684,7 @@ static TranslationBlock *tb_find_pc(uintptr_t tc_ptr) m_min = m + 1; } } - return &tcg_ctx.tb_ctx.tbs[m_max]; + return tcg_ctx.tb_ctx.tbs[m_max]; } #if !defined(CONFIG_USER_ONLY) @@ -1874,7 +1882,7 @@ void dump_exec_info(FILE *f, fprintf_function cpu_fprintf) direct_jmp_count = 0; direct_jmp2_count = 0; for (i = 0; i < tcg_ctx.tb_ctx.nb_tbs; i++) { - tb = &tcg_ctx.tb_ctx.tbs[i]; + tb = tcg_ctx.tb_ctx.tbs[i]; target_code_size += tb->size; if (tb->size > max_target_code_size) { max_target_code_size = tb->size; @@ -1894,8 +1902,7 @@ void dump_exec_info(FILE *f, fprintf_function cpu_fprintf) cpu_fprintf(f, "gen code size %td/%zd\n", tcg_ctx.code_gen_ptr - tcg_ctx.code_gen_buffer, tcg_ctx.code_gen_highwater - tcg_ctx.code_gen_buffer); - cpu_fprintf(f, "TB count %d/%d\n", - tcg_ctx.tb_ctx.nb_tbs, tcg_ctx.code_gen_max_blocks); + cpu_fprintf(f, "TB count %d\n", tcg_ctx.tb_ctx.nb_tbs); cpu_fprintf(f, "TB avg target size %d max=%d bytes\n", tcg_ctx.tb_ctx.nb_tbs ? target_code_size / tcg_ctx.tb_ctx.nb_tbs : 0,