From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=95.215.58.157 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794191579; b=mtuTMKLZZzNoT6k5Dtup5gNukIC+mBrxuCAFngvMQFrq/qW6T+lVwJbJnjnY7DQc1eNk Vam3jaCRMv8IxPBGYfGuq+7VQk+uO3ks/VdH1aYk2bT1OWxLwXLNSgd1FOw1i1GQhjzOx ZFg7dDD8xvuVUzt4jhZneok3zV6KeeSm/6Qg2G63KCfHTRyaC2BSv1kg9OwtJDOw/3xbs J+G/LTWY1zf9/wqfHnYFQDYOW5nKTqN6cDAeA8iAacnZWI2ixZK6V1KpBZK6ZiTXJNkjq /N+w2pVEo4VcW0HYQ+F19efBYvNcnzYHhG9fvVXmGjMK2j43O0FmMfdLD+BpZiDLgVg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794191579; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=NTJQRFg4ZLfC+WrQK17Fwq2xbU+TlVAHwMAwagSHegE=; b=p/WQs80HvTVu1SERkB3pzUbhHxuHTDyfAxxJPOATcYWYsUUzRZdL7so69AVExHOybpV1 +kn7dMdSs0mKXgAhsCVFOyJ+zxkRh24x7SilK008Khbmk7vBpQO0PucHo/nyy5Ndf7lcM PPYSh+uE68d7r3KgtqZIjRTeiuU4GUKKM8y2UThH2OA8Px6DljxFEPMe6p+pR/l9BvNQZ sRyFB24k2oetk5KVTLEzbZ7mCNnCFq/xbI4ui/FAlj6LGF8scLqg8AsThPlP39Basg4Mc Bs9C2Njqepx8lCgRMrt52t9A317QmFdoF8IBvfFNBcFiJlvMYErnseWZm4fdQtb5KDg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=F2gaGqHO; arc=none smtp.remote-ip=95.215.58.157 Received: from mta1.migadu.com (out-157.mta1.migadu.com [95.215.58.157]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 63EE7606A320 for ; Mon, 9 Nov 2026 02:32:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 63EE7606A320 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=F2gaGqHO X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=+0SMLJkywubB1aX8z8chXAoTRSPPEPx3GuRAB7UvFQQ=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1794191576; v=1; x=1794796376; b=F2gaGqHOZ1AzwzNGFTyHvBkAEUf7G89vTgOoeIwbAckvPxfQhqVMkBB2kH3sUGFDcjEKtIGH twNceq0jMlUWbbHmoP6jAGAwuYbnLtgfqPYgo0/JatIYj8+eAiR7KbcPZVs8NZG0Za0JiFI4uze 3JZQGOjOtF/5i7JjuUMbxc6w= X-Envelope-To: linux-kernel@vger.kernel.org Received: by mta12.migadu.com with ESMTPS id 87ec61e94bf44d6f; Mon, 09 Nov 2026 02:32:56 +0000 X-Mizu-Trace-ID: 87ec61e94bf44d6f X-Migadu-Flow: FLOW_OUT Date: Mon, 9 Nov 2026 10:32:45 +0800 From: "Xu Xin (vivo)" To: Qiliang Yuan Cc: Andrew Morton , David Hildenbrand , Chengming Zhou , Stefan Roesch , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Jonathan Corbet , Shuah Khan , Randy Dunlap , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v4 4/5] selftests/mm: move waiting for KSM full scans into a helper Message-ID: References: <20261108-bug-mm-ksm-smart-scan-align-skips-v4-0-86be8fe77e7a@gmail.com> <20261108-bug-mm-ksm-smart-scan-align-skips-v4-4-86be8fe77e7a@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261108-bug-mm-ksm-smart-scan-align-skips-v4-4-86be8fe77e7a@gmail.com> On Sun, Nov 08, 2026 at 08:22:53PM -0500, Qiliang Yuan wrote: > ksm_start() enables ksmd and then polls full_scans until two more full > scans have completed, so that any merging that can happen has happened. > > There is no helper to wait for a number of full scans while ksmd is > already running, so a test that needs one has to copy that loop. > > Move the loop into ksm_wait_full_scans() and make ksm_start() call it > after enabling ksmd. The count is now read after ksmd starts rather than > before, which can only make ksm_start() wait longer. > > Signed-off-by: Qiliang Yuan > Tested-by: Andrew Morton > Reviewed-by: David Hildenbrand (Arm) Reviewed-by: Xu Xin (vivo) > --- > tools/testing/selftests/mm/vm_util.c | 31 ++++++++++++++++++------------- > tools/testing/selftests/mm/vm_util.h | 1 + > 2 files changed, 19 insertions(+), 13 deletions(-) > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index caea045fa7d46..8184691211acc 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -992,35 +992,40 @@ int ksm_use_zero_pages(void) > return ret == 1 ? 0 : -EIO; > } > > +int ksm_wait_full_scans(long nr) > +{ > + long start_scans, end_scans; > + > + start_scans = ksm_get_full_scans(); > + if (start_scans < 0) > + return start_scans; > + do { > + end_scans = ksm_get_full_scans(); > + if (end_scans < 0) > + return end_scans; > + } while (end_scans < start_scans + nr); > + > + return 0; > +} > + > int ksm_start(void) > { > int ksm_fd; > ssize_t ret; > - long start_scans, end_scans; > > ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR); > if (ksm_fd < 0) > return -errno; > > - /* Wait for two full scans such that any possible merging happened. */ > - start_scans = ksm_get_full_scans(); > - if (start_scans < 0) { > - close(ksm_fd); > - return start_scans; > - } > ret = write(ksm_fd, "1", 1); > close(ksm_fd); > if (ret < 0) > return -errno; > if (ret != 1) > return -EIO; > - do { > - end_scans = ksm_get_full_scans(); > - if (end_scans < 0) > - return end_scans; > - } while (end_scans < start_scans + 2); > > - return 0; > + /* Wait for two full scans such that any possible merging happened. */ > + return ksm_wait_full_scans(2); > } > > int ksm_stop(void) > diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h > index b5d59729d4327..7e00030077d2f 100644 > --- a/tools/testing/selftests/mm/vm_util.h > +++ b/tools/testing/selftests/mm/vm_util.h > @@ -162,6 +162,7 @@ void *sys_mremap(void *old_address, unsigned long old_size, > long ksm_get_self_zero_pages(void); > long ksm_get_self_merging_pages(void); > long ksm_get_full_scans(void); > +int ksm_wait_full_scans(long nr); > int ksm_use_zero_pages(void); > int ksm_start(void); > int ksm_stop(void); > > -- > 2.43.0 >