The emacs-lsp-booster project provides a rust-based wrapper program which substantially speeds up emacs' interactions with lsp servers. This small package enables eglot to use it.
Install directly from this repo via M-x package-vc-install (pasting in this URL), or using, e.g. straight. Then, in your init, simply
(use-package eglot-booster
:after eglot
:config (eglot-booster-mode))Then just use eglot as normal. You should notice no differences other than speedier performance and less I/O blocking.
To verify that the wrapper is functioning, M-x eglot-events-buffer and look at the beginning for emacs_lsp_booster::app notices. If you'd like to avoid boosting remote servers (those run over TRAMP), set eglot-booster-no-remote-boost to t.
Important
At present only local or remote (tramp-based) lsp server programs which communicate by standard input/output can be wrapped, not lsp servers communicating over network ports (local or remote). Using remote servers over tramp requires installing emacs-lsp-booster on the remote server.
Maybe you don't even need this. You can M-x eglot-booster to disable the boost at any time. Then M-x eglot-shutdown-all, restart eglot (M-x eglot is usually enough) in a large/heavy-weight file, and compare performance before and after.
emacs-lsp-booster offers the option --disable-bytecode. Setting eglot-booster-io-only=t will use this option, processing JSON as normal. This way you still get the benefit of I/O buffering, but can use Emacs' native JSON parser (which was substantially sped-up in v30).