Clean up some Mac memory code.

base/process/process_metrics.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains routines for gathering resource statistics for processes
 // running on the system.
 
 #ifndef BASE_PROCESS_PROCESS_METRICS_H_
 #define BASE_PROCESS_PROCESS_METRICS_H_
 
@@ skipping 45 matching lines @@
 // priv:           Pages mapped only by this process.
 // shared:         PSS or 0 if the kernel doesn't support this.
 // shareable:      0
 
 // On ChromeOS:
 // priv:           Pages mapped only by this process.
 // shared:         PSS or 0 if the kernel doesn't support this.
 // shareable:      0
 // swapped         Pages swapped out to zram.
 //
-// On OS X: TODO(thakis): Revise.
-// priv:           Memory.
+// On macOS:
+// priv:           Resident size (RSS) including shared memory.

[Alexei Svitkine (slow), 2017/03/29 20:12:26]

Note: based on what the GetCommittedAndWorkingSetKBytes() code.

[erikchen, 2017/03/29 20:25:14]

GetCommittedAndWorkingSetKBytes returns pmap->stats.resident_count
[see osfmk/i386/pmap.h and osfmk/kern/task.c].

This provides an underestimate of RSS [by any reasonable definition]. See
Appendix C under
https://docs.google.com/document/d/1zcfWSsgwTY8WYYlxd0G8QTR6_b2j38uMfjjXBOuMZ...,
look at section titled  "macOS: Use task_info(TASK_VM_INFO, …)".

I've intentionally avoided touching this comment because I want to overhaul this
entire file once my design doc has been fully reviewed.

[Alexei Svitkine (slow), 2017/03/29 21:02:39]

I see - should I just update the TODO to you and reference a crbug then?

Reason I wanted to provide more info is because in the meantime, this is being
used for Memory.Total2 and other metrics and having more info about what that's
counting rather than less is better in the meantime. I could expand my change
here and add a warning about it - similar (but shorter) to what you have in the
doc. WDYT?

[erikchen, 2017/03/29 21:10:38]

You're welcome to add a warning and a more accurate description.

[Alexei Svitkine (slow), 2017/03/29 21:16:54]

Done. PTAL.

 // shared:         0
 // shareable:      0
 //
 struct WorkingSetKBytes {
   WorkingSetKBytes() : priv(0), shareable(0), shared(0) {}
   size_t priv;
   size_t shareable;
   size_t shared;
 #if defined(OS_CHROMEOS)
   size_t swapped;
@@ skipping 381 matching lines @@
   SystemDiskInfo disk_info_;
 #endif
 #if defined(OS_CHROMEOS)
   SwapInfo swap_info_;
 #endif
 };
 
 }  // namespace base
 
 #endif  // BASE_PROCESS_PROCESS_METRICS_H_