[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH] x86/pod: Do not fragment PoD memory allocations
- To: Jan Beulich <jbeulich@xxxxxxxx>, Elliott Mitchell <ehem+xen@xxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Mon, 25 Jan 2021 10:20:19 +0000
- Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none
- Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=KijevWn2ThUgpyKEDfC1tAXfXNNpXXx0x6p5sh5R76k=; b=etNpRI1UbXIaK8M0I9k1+tFlSnvN2RDp74px86QBOAnftv1oyp+Zed/XdLwtyrHNuKQLynTXmvXf/GoDl0nLyCoHuvOHIMXCekCiINgNl5ckIe0P9Fe5FTF2GMTCUy167nuErE0STUIfihPZl46RKTr7v7uMZtwYMvj7yZ26w//KKh2IPnzv+nQt9rJau/KA0+Eoe4MiwXUvUPM5NgYVxzJp/csrCEWpne1e2doEQno3eV0DHay3i4hP52ular7stFuY+ol3Rzqs9CX0TvkkKAyn+BBM8dOMMolsOxQebLkrsMtHlf5PPfkQdI5jRJRFfNzBiCdmHGsKfTq8vdeJSQ==
- Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Nfx49u2qrRPVQMyr5VZ71QSMXEwMGDvHOpmIfS6YP9Z8/u/FplYFaz8lbUO3ZXcEve7fG32SidzPFLAMPM+4BGQCSMxzWJsWp7ozhjaPtT72NlmVM7h4sRHe5KteYFt18J5FdKB/V6rxHJ24BkwdgiCSNLs2iUWgdL3Km7b0LaZDrTPZqeetGo1yP0pMdm0nnwvTe4xB9n0zm9aoNrIu0/mmZCdPOMBpu2Xi7FU112NtJFHDu4Y3r4riBof8+qmc622qfILxarA/eta/a31IlEboYbAs8ju0wDa/SFDJwPgGW6fTO47QidvIj4dNCa5EimIxvlHIXzkgqyr1h9OhKA==
- Authentication-results: esa1.hc3370-68.iphmx.com; dkim=pass (signature verified) header.i=@citrix.onmicrosoft.com
- Cc: George Dunlap <george.dunlap@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 25 Jan 2021 10:20:37 +0000
- Ironport-sdr: vsNkZWSEdtD50yAIwdT9bNrL4jmMuDSYFBkMO7Rplk/qJH2uSTiTVo5P6H7JFHZftC7dLGPPNz 4JHEwE4G5RZaWoRDI5+WJS2FgQsyot/WC8OBp1Xec17+GtHNOVJKvoqIkFd/1RdI0aEly2wVK2 JPUiI5NKOrmaZJ5TVziTxPDOSZI3yntgpOhHPGsEDBvXPeAIjLjaNi9XWkduOcie5y9WUyUq2m dS2y/3R/BWlHAnq3R1i5lcGMbYognOawp5Mpc/1OE5jdrgzlyk1W1JRDkJwk+/8OeYkgwIRUlw uFo=
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25/01/2021 09:56, Jan Beulich wrote:
> On 24.01.2021 05:47, Elliott Mitchell wrote:
>> Previously p2m_pod_set_cache_target() would fall back to allocating 4KB
>> pages if 2MB pages ran out. This is counterproductive since it suggests
>> severe memory pressure and is likely a precursor to a memory exhaustion
>> panic. As such don't try to fill requests for 2MB pages from 4KB pages
>> if 2MB pages run out.
> I disagree - there may be ample 4k pages available, yet no 2Mb
> ones at all. I only agree that this _may_ be counterproductive
> _if indeed_ the system is short on memory.
Further to this, PoD is very frequently used in combination with
ballooning operations, in which case there are (or can be made to be)
plenty of 4k pages, even without a single 2M range in sight.
~Andrew
|
