From patchwork Mon Jan 20 16:27:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11342477 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3AD22921 for ; Mon, 20 Jan 2020 16:28:53 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E14462253D for ; Mon, 20 Jan 2020 16:28:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="EboO3ROQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E14462253D Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=amazon.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E04FB6B067C; Mon, 20 Jan 2020 11:28:51 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id DB76C6B067D; Mon, 20 Jan 2020 11:28:51 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C7D256B0680; Mon, 20 Jan 2020 11:28:51 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0006.hostedemail.com [216.40.44.6]) by kanga.kvack.org (Postfix) with ESMTP id A7D586B067C for ; Mon, 20 Jan 2020 11:28:51 -0500 (EST) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 6A77A824805A for ; Mon, 20 Jan 2020 16:28:51 +0000 (UTC) X-FDA: 76398546462.30.bee16_6a5fbc1247547 X-Spam-Summary: 1,0,0,,d41d8cd98f00b204,prvs=2817cd025=sjpark@amazon.com,:akpm@linux-foundation.org:sjpark@amazon.de:acme@kernel.org:brendan.d.gregg@gmail.com:corbet@lwn.net:mgorman@suse.de:dwmw@amazon.com:amit@kernel.org:rostedt@goodmis.org:sj38.park@gmail.com::linux-doc@vger.kernel.org:linux-kernel@vger.kernel.org,RULES_HIT:30003:30012:30034:30051:30054:30056:30064:30070:30075,0,RBL:52.95.49.90:@amazon.com:.lbl8.mailshell.net-62.18.0.100 64.10.201.10,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:24,LUA_SUMMARY:none X-HE-Tag: bee16_6a5fbc1247547 X-Filterd-Recvd-Size: 21082 Received: from smtp-fw-6002.amazon.com (smtp-fw-6002.amazon.com [52.95.49.90]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Mon, 20 Jan 2020 16:28:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1579537731; x=1611073731; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=AJE8BG+QL3Cg36CWDr/yFzXVt0uQE0xPlNoyGI9RMlE=; b=EboO3ROQm5+23OS7oN+/FrUU1iWYxrsDBQklLyJFcwmsTJ4HhihUn/l8 0vYY6yAj4wIbRKlYj2VLPMUQu7zHtkm2CB6usNq9MieqHz9hiBHu4eDsN UQ3D09cs0dysG69GKA+eeOS8EOxYiDxsVO6b7bfxiqIYiPOLGXbbltpwE Y=; IronPort-SDR: Ky++joz7XMZtPFARfkZGbRffeg/edz42TRSL8i523W1oa9QYps0O4ye3xWMRFt3x094MyzuV3N vPcgp4A10zmw== X-IronPort-AV: E=Sophos;i="5.70,342,1574121600"; d="scan'208";a="12341457" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-2a-538b0bfb.us-west-2.amazon.com) ([10.43.8.6]) by smtp-border-fw-out-6002.iad6.amazon.com with ESMTP; 20 Jan 2020 16:28:48 +0000 Received: from EX13MTAUEA002.ant.amazon.com (pdx4-ws-svc-p6-lb7-vlan3.pdx.amazon.com [10.170.41.166]) by email-inbound-relay-2a-538b0bfb.us-west-2.amazon.com (Postfix) with ESMTPS id 2CFEDA06C2; Mon, 20 Jan 2020 16:28:47 +0000 (UTC) Received: from EX13D31EUA001.ant.amazon.com (10.43.165.15) by EX13MTAUEA002.ant.amazon.com (10.43.61.77) with Microsoft SMTP Server (TLS) id 15.0.1236.3; Mon, 20 Jan 2020 16:28:46 +0000 Received: from u886c93fd17d25d.ant.amazon.com (10.43.161.253) by EX13D31EUA001.ant.amazon.com (10.43.165.15) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Mon, 20 Jan 2020 16:28:40 +0000 From: SeongJae Park To: CC: SeongJae Park , , , , , , , , , , , Subject: [PATCH 2/8] mm/damon: Implement region based sampling Date: Mon, 20 Jan 2020 17:27:51 +0100 Message-ID: <20200120162757.32375-3-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200120162757.32375-1-sjpark@amazon.com> References: <20200120162757.32375-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.161.253] X-ClientProxiedBy: EX13D14UWC002.ant.amazon.com (10.43.162.214) To EX13D31EUA001.ant.amazon.com (10.43.165.15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: SeongJae Park This commit implements DAMON's basic access check and region based sampling mechanisms. Basic Access Check ------------------ DAMON basically reports what pages are how frequently accessed. Note that the frequency is not an absolute number of accesses, but a relative frequency among the pages of the target workloads. Users can control the resolution of the reports by setting two time intervals, ``sampling interval`` and ``aggregation interval``. In detail, DAMON checks access to each page per ``sampling interval``, aggregates the results (counts the number of the accesses to each page), and reports the aggregated results per ``aggregation interval``. For the access check of each page, DAMON uses the Accessed bits of PTEs. This is thus similar to common periodic access checks based access tracking mechanisms, which overhead is increasing as the size of the target process grows. Region Based Sampling --------------------- To avoid the unbounded increase of the overhead, DAMON groups a number of adjacent pages that assumed to have same access frequencies into a region. As long as the assumption (pages in a region have same access frequencies) is kept, only one page in the region is required to be checked. Thus, for each ``sampling interval``, DAMON randomly picks one page in each region and clears its Accessed bit. After one more ``sampling interval``, DAMON reads the Accessed bit of the page and increases the access frequency of the region if the bit has set meanwhile. Therefore, the monitoring overhead is controllable by setting the number of regions. Nonetheless, this scheme cannot preserve the quality of the output if the assumption is not kept. Signed-off-by: SeongJae Park --- mm/damon.c | 599 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 599 insertions(+) diff --git a/mm/damon.c b/mm/damon.c index 064ec1f6ded9..2a0c010291f8 100644 --- a/mm/damon.c +++ b/mm/damon.c @@ -9,9 +9,14 @@ #define pr_fmt(fmt) "damon: " fmt +#include +#include #include #include +#include #include +#include +#include #include #define damon_get_task_struct(t) \ @@ -54,6 +59,36 @@ struct damon_task { /* List of damon_task objects */ static LIST_HEAD(damon_tasks_list); +/* + * For each 'sample_interval', DAMON checks whether each region is accessed or + * not. It aggregates and keeps the access information (number of accesses to + * each region) for 'aggr_interval' and then flushes it to the result buffer if + * an 'aggr_interval' surpassed. + * + * All time intervals are in micro-seconds. + */ +static unsigned long sample_interval = 5 * 1000; +static unsigned long aggr_interval = 100 * 1000; + +static struct timespec64 last_aggregate_time; + +static unsigned long min_nr_regions = 10; + +/* result buffer */ +#define DAMON_LEN_RBUF (1024 * 1024 * 4) +static char damon_rbuf[DAMON_LEN_RBUF]; +static unsigned int damon_rbuf_offset; + +/* result file */ +#define LEN_RES_FILE_PATH 256 +static char rfile_path[LEN_RES_FILE_PATH] = "/damon.data"; + +static struct task_struct *kdamond; +static bool kdamond_stop; + +/* Protects read/write of kdamond and kdamond_stop */ +static DEFINE_SPINLOCK(kdamond_lock); + static struct rnd_state rndseed; /* Get a random number in [l, r) */ #define damon_rand(l, r) (l + prandom_u32_state(&rndseed) % (r - l)) @@ -202,16 +237,580 @@ static unsigned int nr_damon_regions(struct damon_task *t) return ret; } +/* + * Get the mm_struct of the given task + * + * Callser should put the mm_struct after use, unless it is NULL. + * + * Returns the mm_struct of the task on success, NULL on failure + */ +static struct mm_struct *damon_get_mm(struct damon_task *t) +{ + struct task_struct *task; + struct mm_struct *mm; + + task = damon_get_task_struct(t); + if (!task) + return NULL; + + mm = get_task_mm(task); + put_task_struct(task); + return mm; +} + +/* + * Size-evenly split a region into 'nr_pieces' small regions + * + * Returns 0 on success, or negative error code otherwise. + */ +static int damon_split_region_evenly(struct damon_region *r, + unsigned int nr_pieces) +{ + unsigned long sz_orig, sz_piece, orig_end; + struct damon_region *piece = NULL, *next; + unsigned long start; + + if (!r || !nr_pieces) + return -EINVAL; + + orig_end = r->vm_end; + sz_orig = r->vm_end - r->vm_start; + sz_piece = sz_orig / nr_pieces; + + if (!sz_piece) + return -EINVAL; + + r->vm_end = r->vm_start + sz_piece; + next = damon_next_region(r); + for (start = r->vm_end; start + sz_piece <= orig_end; + start += sz_piece) { + piece = damon_new_region(start, start + sz_piece); + damon_add_region(piece, r, next); + r = piece; + } + if (piece) + piece->vm_end = orig_end; + return 0; +} + +struct region { + unsigned long start; + unsigned long end; +}; + +static unsigned long sz_region(struct region *r) +{ + return r->end - r->start; +} + +static void swap_regions(struct region *r1, struct region *r2) +{ + struct region tmp; + + tmp = *r1; + *r1 = *r2; + *r2 = tmp; +} + +/* + * Find the three regions in an address space + * + * vma the head vma of the target address space + * regions an array of three 'struct region's that results will be saved + * + * This function receives an address space and finds three regions in it which + * separated by the two biggest unmapped regions in the space. + * + * Returns 0 if success, or negative error code otherwise. + */ +static int damon_three_regions_in_vmas(struct vm_area_struct *vma, + struct region regions[3]) +{ + struct region gap = {0,}, first_gap = {0,}, second_gap = {0,}; + struct vm_area_struct *last_vma = NULL; + unsigned long start = 0; + + /* Find two biggest gaps so that first_gap > second_gap > others */ + for (; vma; vma = vma->vm_next) { + if (!last_vma) { + start = vma->vm_start; + last_vma = vma; + continue; + } + gap.start = last_vma->vm_end; + gap.end = vma->vm_start; + if (sz_region(&gap) > sz_region(&second_gap)) { + swap_regions(&gap, &second_gap); + if (sz_region(&second_gap) > sz_region(&first_gap)) + swap_regions(&second_gap, &first_gap); + } + last_vma = vma; + } + + if (!sz_region(&second_gap) || !sz_region(&first_gap)) + return -EINVAL; + + /* Sort the two biggest gaps by address */ + if (first_gap.start > second_gap.start) + swap_regions(&first_gap, &second_gap); + + /* Store the result */ + regions[0].start = start; + regions[0].end = first_gap.start; + regions[1].start = first_gap.end; + regions[1].end = second_gap.start; + regions[2].start = second_gap.end; + regions[2].end = last_vma->vm_end; + + return 0; +} + +/* + * Get the three regions in the given task + * + * Returns 0 on success, negative error code otherwise. + */ +static int damon_three_regions_of(struct damon_task *t, + struct region regions[3]) +{ + struct mm_struct *mm; + int ret; + + mm = damon_get_mm(t); + if (!mm) + return -EINVAL; + + down_read(&mm->mmap_sem); + ret = damon_three_regions_in_vmas(mm->mmap, regions); + up_read(&mm->mmap_sem); + + mmput(mm); + return ret; +} + +/* + * Initialize the monitoring target regions for the given task + * + * t the given target task + * + * Because only a number of small portions of the entire address space + * is acutally mapped to the memory and accessed, monitoring the unmapped + * regions is wasteful. That said, because we can deal with small noises, + * tracking every mapping is not strictly required but could even incur a high + * overhead if the mapping frequently changes or the number of mappings is + * high. + * + * As usual memory map of processes is as below, the gap between the heap and + * the uppermost mmap()-ed region, and the gap between the lowermost mmap()-ed + * region and the stack will be two biggest unmapped regions. Because these + * gaps are outliers between the mapped and unmapped regions in the address + * space in terms of the size, excluding these two biggest unmapped regions + * will be sufficient to make a trade-off. + * + * + * + * + * (other mmap()-ed regions and small unmapped regions) + * + * + * + * + * For the reason, this function converts the original address space of the + * given task to a simplified address space, that is constructed with three + * regions separated by the two biggest unmapped regions and stores those in + * the given task. + */ +static void damon_init_regions_of(struct damon_task *t) +{ + struct damon_region *r; + struct region regions[3]; + int i; + + if (damon_three_regions_of(t, regions)) { + pr_err("Failed to get three regions of task %lu\n", t->pid); + return; + } + + /* Set the initial three regions of the task */ + for (i = 0; i < 3; i++) { + r = damon_new_region(regions[i].start, regions[i].end); + damon_add_region_tail(r, t); + } + + /* Split the middle region into 'min_nr_regions - 2' regions */ + r = damon_nth_region_of(t, 1); + if (damon_split_region_evenly(r, min_nr_regions - 2)) + pr_warn("Init middle region failed to be split\n"); +} + +/* Initialize '->regions_list' of every task */ +static void kdamond_init_regions(void) +{ + struct damon_task *t; + + damon_for_each_task(t) + damon_init_regions_of(t); +} + +/* + * Check whether the given region has accessed since the last check + * + * mm 'mm_struct' for the given virtual address space + * r the region to be checked + */ +static void kdamond_check_access(struct mm_struct *mm, struct damon_region *r) +{ + pte_t *pte = NULL; + pmd_t *pmd = NULL; + spinlock_t *ptl; + + if (follow_pte_pmd(mm, r->sampling_addr, NULL, &pte, &pmd, &ptl)) + goto mkold; + + /* Read the page table access bit of the page */ + if (pte && pte_young(*pte)) + r->nr_accesses++; +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + else if (pmd && pmd_young(*pmd)) + r->nr_accesses++; +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + + spin_unlock(ptl); + +mkold: + /* mkold next target */ + r->sampling_addr = damon_rand(r->vm_start, r->vm_end); + + if (follow_pte_pmd(mm, r->sampling_addr, NULL, &pte, &pmd, &ptl)) + return; + + if (pte) { + if (pte_young(*pte)) + clear_page_idle(pte_page(*pte)); + *pte = pte_mkold(*pte); + } +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + else if (pmd) { + if (pmd_young(*pmd)) + clear_page_idle(pmd_page(*pmd)); + *pmd = pmd_mkold(*pmd); + } +#endif + + spin_unlock(ptl); +} + +/* + * Check whether a time interval is elapsed + * + * baseline the time to check whether the interval has elapsed since + * interval the time interval (microseconds) + * + * See whether the given time interval has passed since the given baseline + * time. If so, it also updates the baseline to current time for next check. + * + * Returns true if the time interval has passed, or false otherwise. + */ +static bool damon_check_reset_time_interval(struct timespec64 *baseline, + unsigned long interval) +{ + struct timespec64 now; + + ktime_get_coarse_ts64(&now); + if ((timespec64_to_ns(&now) - timespec64_to_ns(baseline)) / 1000 < + interval) + return false; + *baseline = now; + return true; +} + +/* + * Check whether it is time to flush the aggregated information + */ +static bool kdamond_aggregate_interval_passed(void) +{ + return damon_check_reset_time_interval(&last_aggregate_time, + aggr_interval); +} + +/* + * Flush the content in the result buffer to the result file + */ +static void damon_flush_rbuffer(void) +{ + ssize_t sz; + loff_t pos; + struct file *rfile; + + while (damon_rbuf_offset) { + pos = 0; + rfile = filp_open(rfile_path, O_CREAT | O_RDWR | O_APPEND, + 0644); + if (IS_ERR(rfile)) { + pr_err("Cannot open the result file %s\n", rfile_path); + return; + } + + sz = kernel_write(rfile, damon_rbuf, damon_rbuf_offset, &pos); + filp_close(rfile, NULL); + + damon_rbuf_offset -= sz; + } +} + +/* + * Write a data into the result buffer + */ +static void damon_write_rbuf(void *data, ssize_t size) +{ + if (damon_rbuf_offset + size > DAMON_LEN_RBUF) + damon_flush_rbuffer(); + + memcpy(&damon_rbuf[damon_rbuf_offset], data, size); + damon_rbuf_offset += size; +} + +/* + * Flush the aggregated monitoring results to the result buffer + * + * Stores current tracking results to the result buffer and reset 'nr_accesses' + * of each regions. The format for the result buffer is as below: + * + *