<p>One last note: doing fdatasync once, before fadvise+fsync, not after every write is ~10x faster:</p>
<p><code>FDIO: 30 writes, 3763601 total bytes in 0.003558 secs FDIO: 1 allocs, 3763601 total bytes in 0.000024 secs FDIO: 1 dsyncs, 0 total bytes in 0.074081 secs FDIO: 1 syncs, 0 total bytes in 0.005785 secs</code></p>
<p>That makes the best case ~17x slower than using the kernel caches. A cost of 17x is almost tolerable in RPM for the benefits of having files written to disk and not blowing out the kernel caches.</p>

<p style="font-size:small;-webkit-text-size-adjust:none;color:#666;">—<br />You are receiving this because you are subscribed to this thread.<br />Reply to this email directly, <a href="https://github.com/rpm-software-management/rpm/pull/187#issuecomment-294217202">view it on GitHub</a>, or <a href="https://github.com/notifications/unsubscribe-auth/ANb804eEBH4kcC2Gi8gfcsifX2oaAgAcks5rv8VCgaJpZM4MyLOi">mute the thread</a>.<img alt="" height="1" src="https://github.com/notifications/beacon/ANb800irwvTOjzHZ5_qjYFxG8T7rDPa4ks5rv8VCgaJpZM4MyLOi.gif" width="1" /></p>
<div itemscope itemtype="http://schema.org/EmailMessage">
<div itemprop="action" itemscope itemtype="http://schema.org/ViewAction">
  <link itemprop="url" href="https://github.com/rpm-software-management/rpm/pull/187#issuecomment-294217202"></link>
  <meta itemprop="name" content="View Pull Request"></meta>
</div>
<meta itemprop="description" content="View this Pull Request on GitHub"></meta>
</div>

<script type="application/json" data-scope="inboxmarkup">{"api_version":"1.0","publisher":{"api_key":"05dde50f1d1a384dd78767c55493e4bb","name":"GitHub"},"entity":{"external_key":"github/rpm-software-management/rpm","title":"rpm-software-management/rpm","subtitle":"GitHub repository","main_image_url":"https://cloud.githubusercontent.com/assets/143418/17495839/a5054eac-5d88-11e6-95fc-7290892c7bb5.png","avatar_image_url":"https://cloud.githubusercontent.com/assets/143418/15842166/7c72db34-2c0b-11e6-9aed-b52498112777.png","action":{"name":"Open in GitHub","url":"https://github.com/rpm-software-management/rpm"}},"updates":{"snippets":[{"icon":"PERSON","message":"@n3npq in #187: One last note: doing fdatasync once, before fadvise+fsync, not after every write is ~10x faster:\r\n\r\n`\r\nFDIO:      30 writes,  3763601 total bytes in 0.003558 secs\r\n FDIO:       1 allocs,  3763601 total bytes in 0.000024 secs\r\n FDIO:       1 dsyncs,        0 total bytes in 0.074081 secs\r\n FDIO:       1  syncs,        0 total bytes in 0.005785 secs\r\n`\r\n\r\nThat makes the best case ~17x slower than using the kernel caches. A cost of 17x is almost tolerable in RPM for the benefits of having files written to disk and not blowing out the kernel caches."}],"action":{"name":"View Pull Request","url":"https://github.com/rpm-software-management/rpm/pull/187#issuecomment-294217202"}}}</script>