From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:38835 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756013AbaHVNFU (ORCPT ); Fri, 22 Aug 2014 09:05:20 -0400 To: Chris Murphy Cc: Btrfs BTRFS Subject: Re: mkfs.btrfs vs fstrim on an SD Card (not SSD) From: "Martin K. Petersen" References: <3CE6F328-8757-4B7F-858F-E820DFDF97E8@colorremedies.com> Date: Fri, 22 Aug 2014 09:04:45 -0400 In-Reply-To: (Chris Murphy's message of "Thu, 21 Aug 2014 21:19:00 -0600") Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-btrfs-owner@vger.kernel.org List-ID: >>>>> "Chris" == Chris Murphy writes: Chris> Since the SD Card spec references a completely different command Chris> than the ATA spec (TRIM), I don't think either one of these are Chris> TRIM, even if functionally equivalent. Instead the SD Card Chris> ERASE_* commands are probably being used, Indeed. Discard is our generic block layer abstraction that gets translated into whichever command is appropriate for the device in question (ACS DSM TRIM, SBC WRITE SAME/UNMAP, etc.). Chris> but I can't confirm this because writes to /dev/mmcblk0 aren't Chris> showing up with: Chris> echo scsi:scsi_dispatch_cmd_start > Chris> /sys/kernel/debug/tracing/set_event echo 1 > Chris> /sys/kernel/debug/tracing/tracing_on cat Chris> /sys/kernel/debug/tracing/trace_pipe MMC doesn't go through SCSI like ATA does. -- Martin K. Petersen Oracle Linux Engineering