Make Linux cache flushing observable

psync makes sync progress visible.

The standard sync command blocks until dirty pages are written without showing what remains. Psync polls Linux write-back counters while sync runs, reports elapsed time and a summary, and can watch a scoped target and resync when its files change.

go install codeberg.org/ubunatic/psync@latest

Install psync View source

Project snapshot · measured 2026-10-26

Key facts

Commits 43Last commit 2026-10-25 Source receipt ↗ Commits · 7 days 5 Source receipt ↗ Tickets closed 3 / 20 Source receipt ↗ Studies 2 Source receipt ↗

12-week commit activity

2026-10-26

Aug 3

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View 12-week data table

Week starting	Commits
2026-08-03	0
2026-08-10	0
2026-08-17	0
2026-08-24	2
2026-08-31	2
2026-09-07	16
2026-09-14	0
2026-09-21	0
2026-09-28	6
2026-10-05	2
2026-10-12	0
2026-10-19	1

Key Features

Shows live progress as Linux writes cached file data to storage during `sync`.
Watch mode reports pending writes and per-device disk activity without starting `sync`.
Follow mode watches selected files and runs `sync` again when they change.
Choose a mounted filesystem interactively, or use a plain prompt without a terminal.

Verified Engineering Milestones

Follow mode and mount picker in the first release (#006, f792678)
Per-device progress in watch mode (#011, 9279f9c)
Loom mount picker and v0.2.2 release (#013, 4485b28, 460d911)

Stack

Go 1.26.5, Cobra, Loom, Linux /proc (meminfo, diskstats, mountinfo), inotify, GoReleaser

Overview

Observe the flush while it runs

Psync starts sync(1) in the background and polls Dirty and Writeback in /proc/meminfo. It prints live progress and a completion summary without changing sync's behavior. Linux per-device write rates and in-flight requests are available when a target mount or device is selected.

psync -f /mnt/secure
psync -w /mnt/secure
psync -F important-file.db

Capabilities

Progress, watch, and scoped follow mode

Sync with progress

Poll system dirty/write-back counters while sync runs and print a summary.

Passive watch

Watch system write-back state without starting sync; target mode also reports device I/O.

Follow changed files

Resync a specific file or directory after changes, with debounce and minimum-interval guards.

Select a mount

Choose a mounted filesystem interactively when follow or watch mode needs a target.

Modes and options

Choose what psync observes

Default

Run sync and show live dirty/write-back progress and a completion summary.

-d / --data

Pass data-only mode to sync(1), without unneeded metadata.

-f / --file-system

Sync the filesystem that contains the selected target files.

-w / --watch

Observe write-back progress without calling sync(1).

-F / --follow

Watch selected files or direct directory entries and resync on changes.

--debounce and --min-interval

Coalesce change bursts and enforce a minimum delay between follow-mode syncs.

-i / --interval

Set how often psync samples /proc/meminfo; the default is 500 ms.

Safe follow mode

Follow only a target you choose

Follow mode requires a scoped file, directory, or selected filesystem. It does not infer targets from system-wide Dirty counters, so unrelated writes from other processes cannot trigger extra sync cycles. Directory watching is non-recursive.

Use psync demo to watch a deterministic simulated flush without writing test data to disk.

psync demo
psync demo --size-mb 8192 --duration 20s

Quickstart

Install and try the simulation

Install from the latest Go module or download a release binary. Run psync demo to see the progress display without root access, a slow disk, or real disk writes.

go install codeberg.org/ubunatic/psync@latest
psync demo

Engineering story

Make Linux sync progress visible

Read the engineering story for the design of live write-back monitoring and scoped follow mode.

Project details

Stack

Go 1.26.5, Cobra, Loom, Linux /proc (meminfo, diskstats, mountinfo), inotify, GoReleaser

Milestones

Follow mode and mount picker in the first release (#006, f792678) · Per-device progress in watch mode (#011, 9279f9c) · Loom mount picker and v0.2.2 release (#013, 4485b28, 460d911)

Source

https://codeberg.org/ubunatic/psync ↗

Architecture

Layer composition

Terminal: CLI, live progress, TUI picker
Desktop: Linux, /proc, inotify
Inference / AI: —
Containers / VM: —
Web: —

Engineering story

psync: the story behind the project

sync(1) is one of those commands whose silence is easy to mistake for a hang. It waits for dirty data in the Linux kernel's page cache to reach storage, but gives the person at the terminal no estimate of progress or throughput. psync wraps…

Read the engineering story

Measurement source · 2026-10-26

Verification receipts

Commits: 43 · Last commit 2026-10-25
git -C <repo> rev-list --count HEAD; git -C <repo> rev-list --count --since=<ISO-week-Monday> --until=<ISO-week-Sunday> HEAD; git -C <repo> rev-list --count --since=<measured-date-6-days>T00:00:00 --until=<measured-date>T23:59:59 HEAD; git -C <repo> log -1 --format=%cs HEAD; ls <repo>/issues | grep '^[0-9].*\.md$'; grep -l -E '^\*\*Status\*\*: *(Closed|Done|Resolved|Fixed|Complete)' <repo>/issues/*.md | wc -l; ls <repo>/docs/studies/*.md
repositories behind spec project ids in ~/projects; private-repo filter is a safety net and matches no spec project today; missing repos reported separately; seven calendar days ending on measured date in the measuring host's local timezone; commit counts include all authors and merge commits reachable from HEAD · measured 2026-10-26
Commits · 7 days: 5
git -C <repo> rev-list --count HEAD; git -C <repo> rev-list --count --since=<ISO-week-Monday> --until=<ISO-week-Sunday> HEAD; git -C <repo> rev-list --count --since=<measured-date-6-days>T00:00:00 --until=<measured-date>T23:59:59 HEAD; git -C <repo> log -1 --format=%cs HEAD; ls <repo>/issues | grep '^[0-9].*\.md$'; grep -l -E '^\*\*Status\*\*: *(Closed|Done|Resolved|Fixed|Complete)' <repo>/issues/*.md | wc -l; ls <repo>/docs/studies/*.md
repositories behind spec project ids in ~/projects; private-repo filter is a safety net and matches no spec project today; missing repos reported separately; seven calendar days ending on measured date in the measuring host's local timezone; commit counts include all authors and merge commits reachable from HEAD · measured 2026-10-26
Tickets closed: 3 / 20
git -C <repo> rev-list --count HEAD; git -C <repo> rev-list --count --since=<ISO-week-Monday> --until=<ISO-week-Sunday> HEAD; git -C <repo> rev-list --count --since=<measured-date-6-days>T00:00:00 --until=<measured-date>T23:59:59 HEAD; git -C <repo> log -1 --format=%cs HEAD; ls <repo>/issues | grep '^[0-9].*\.md$'; grep -l -E '^\*\*Status\*\*: *(Closed|Done|Resolved|Fixed|Complete)' <repo>/issues/*.md | wc -l; ls <repo>/docs/studies/*.md
repositories behind spec project ids in ~/projects; private-repo filter is a safety net and matches no spec project today; missing repos reported separately; seven calendar days ending on measured date in the measuring host's local timezone; commit counts include all authors and merge commits reachable from HEAD · measured 2026-10-26
Studies: 2
git -C <repo> rev-list --count HEAD; git -C <repo> rev-list --count --since=<ISO-week-Monday> --until=<ISO-week-Sunday> HEAD; git -C <repo> rev-list --count --since=<measured-date-6-days>T00:00:00 --until=<measured-date>T23:59:59 HEAD; git -C <repo> log -1 --format=%cs HEAD; ls <repo>/issues | grep '^[0-9].*\.md$'; grep -l -E '^\*\*Status\*\*: *(Closed|Done|Resolved|Fixed|Complete)' <repo>/issues/*.md | wc -l; ls <repo>/docs/studies/*.md
repositories behind spec project ids in ~/projects; private-repo filter is a safety net and matches no spec project today; missing repos reported separately; seven calendar days ending on measured date in the measuring host's local timezone; commit counts include all authors and merge commits reachable from HEAD · measured 2026-10-26
12-week commit activity
git rev-list --count --since=<Monday> --until=<Sunday> HEAD
12 latest complete ISO weeks; weekly values are from spec/metrics.yaml.